… say you have two accounts for one site – then you would rather let Bitwarden decide (randomly?) to only offer you one of those two items to update instead of deciding/assessing for yourself which one of the two items you “updated”?
PS: Suggestion: add some more details to your first post – or a following one. It’s a bit impractical for everyone participating to have to look into that GitHub for discussing it here.
PPS:
Expected Result
It should allow the users to click both update buttons.
… but then both your items would be identical, wouldn’t they…?!? – And then: why have two different/separate items in the first place, when they are identical? 
@jidanni The problem you’ve described would be better solved by not using two separate vault items for beitun.taichung.gov.tw and civil.taichung.gov.tw. If the two websites use the same username (積丹尼) and the same password, then you should use a single vault item that contains both URLs.
All I know is that’s how they ended up. I never go and edit items. They just get that way through day to day usage, or perhaps an initial import. But it doesn’t matter, how they ended up that way, it is a clear bug to ask two things at once, and then exit the dialog upon any answer. Furthermore, I suppose a bot decided that this was intended behaviour.
So one day this double headed box comes up,
I click one of the buttons (hey, I only have one mouse),
and I get the message “updated that item”, and the box closes.
What about the other item?
Why didn’t it give me the chance to click that?
Why is this “intended behaviour”?
Well, I don’t know Bitwarden’s motives here… but my interpretation would be: that update prompt assumes that you don’t have duplicate/identical login items in your vault, but instead maybe two (or more) different items, that is: different accounts for one service. And if you changed username/email and/or password for one account, you most likely only want to update this one corresponding item in your vault – and not the different one also.
I think I don’t have any duplicate items in my entire vault, but for some services more than one login item (like a few distinct login items for a few different Google accounts).
What would be the “intended use case” for identical (duplicate) login items in your vault?
PS:
I really don’t think it’s a bug, as there are use cases for that scenario.
I really don’t think @rmcdowell is a bot. 
If the problem of redundant entries being generated is bothersome to you, then you may wish to explore what it is about your work habits that causes the problem, and consider changing those habits. As an example, I personally never encounter any unexpected/unwanted items in my Bitwarden vault, so this issue does not afflict all users.
In that case, cleaning up your vault may be in order (again, if the problem of redundant entries is bothersome to you).
I think that the “intended behavior” is based on the assumption that users do not keep redundant login items in their vault. The reason why multiple matching items are shown at all is likely because two unrelated login items may match to the active website if the user is using non-stringent URI match detection methods (e.g., “Base Domain”) — e.g. a user may have separate login items for community.bitwarden.com and vault.bitwarden.com, and Bitwarden would offer both options if the matching is set to “Base Domain” and if the username is the same for both sites.
Here it is asking again about many items. Notice the slider.
If I click one of those update buttons, I get a message that that item got updated, and the dialog closes.
Therefore the user is only allowed to update one item.
This proves that there is a 100% design blunder!!!
It doesn’t matter about my work habits.
It doesn’t matter about my preferences.
It is just like if I go to a restaurant,
and there are lots of things on the menu.
And I pick a salad, and before I can also choose a soup,
poof, the menu gets whisked away by the garçon, and that’s all I get to eat tonight.
Not really. For example, the two logins shown in your screenshot seem to be two unrelated accounts, as they have different usernames (“jidanni” and “b”, respectively). In that case, the two login items should not be using the same password, to mitigate the risk of credential stuffing attacks; thus, if you update one of those two login items, you should not also be updating the other one (with the same password).
When it comes to the remaining logins in that list (viewable by scrolling), if any of them actually are duplicate entries representing the same account, then the intended behavior (from users!) is to consolidate those vault items.
This is not a bug, but you might want to raise a feature request to propose additional flexibility in the Update Existing Account feature.
For what’s worth, i tend to agree with @jidanni that this is a bug.
BW is showing me a list of accounts to update, because BW somehow decided all those accounts are related to this website i updated my password. Therefore, BW must let me click Update for any, including all, including none (that’s the X button of the popup for).
To reiterate the technicality why i think BW must let me update multiple: BW is the one showing me that multiple of my password entries are related to this website. If you show me multiple options, then let me edit them all.
BTW I discovered if I click fast enough, I can update both entries in the little window.
At least that’s what the success message said.
Anyway, perhaps the moderator could move this thread to the bugs group and make a better title for it. Thanks.
Somehow? Well, one deciding factor for this is: same URL in those login items. It’s not completely random…
Well, I think in general I would agree with @grb and this should be made a feature request… but it would be a somewhat dangerous option, IMHO. – Example:
I have five Google accounts in my vault: my original Google account, two “test” accounts, and the two accounts of my parents. Each of those five accounts has a separate email address (obviously) and a unique password. – Let’s say I now want to use my own main Google account, and regardless if I get the update prompt for a changed username/email or password: As all five different Google accounts are presented to me in that update prompt, I would destroy those four other Google accounts in my vault if I updated all five. (with either a then-wrong email address or then-wrong password)
I would if I could. There really is no dedicated “bug section” in the forum. As tried before, bugs are reported on GitHub. Either try it a second time with better arguments - or indeed, open a feature request. (assuming there is none)
(emphasis added)
This is precisely what determines that it is not a bug: Bitwarden decided that it should work like this, so it is expected behavior. If you feel that that the expected behavior is unsatisfactory, then open a Feature Request to propose an improvement to the current functionality.
Now, that, on the other hand, looks like a bug! This behavior is unlikely to be intentional (i.e., by design), so it would be considered unexpected behavior and treated as a bug (if reported on Github).
The point i was trying to make is the way BW figures out the list of multiple accounts is irrelevant for the discussion at hand. I though somehow was a good word. Maybe it isn’t?
I have five Google accounts in my vault
[…]
As all five different Google accounts are presented to me in that update prompt
You don’t need to update all 5. You use your judgement to decide which account to update. But you should be allowed to update multiple accounts if that’s the correct thing to do.
Currently you have no choice. You can update 0 accounts or 1 account. NO MORE.
(caps rage for emphasis. I’m not yelling at anyone. <3 you all)
That can only be the correct thing to do, if you have duplicates in your vault. I see your point, but I would rather try to get rid of any duplicates first (and support this feature request: Duplicate removal tool/report (including merge)), as identical vault entries don’t serve any purpose.
But…
… as I already also wrote: make a feature request, if it is important to you! 
Every time I open an issue on Github it’s like
So I think it’s time for me to leave this in the hands of you pros. See ya.
Thanks for that clip – but in all transparency: I won’t open a feature request about that…
… ah, and maybe one tip: if you really wanted (all along) to be able to “update all items at once”… then maybe don’t choose “Don’t ask user to update more than one at a time” as a title next time…
@jidanni I now tried to give that thread a better title at least (original one was Intended behaviour?). If you object to my suggestion, please express it and I’ll adjust it.