If i can understood your problem correctly you are facing issues with switching the user account while doing an autofill through the android app redirect.
I think this issue is somewhat genuine, i tested it out and it does seem to redirect you to the current switched account, with no way to switch to the other account without exiting the current session and manually setting the app to desired profile.
I guess account switching feature is relatively newer in the android app as it was released with version 2.17.0 , so we can expect improvement with subsequent releases which might fix it.
It think your case could provide a valuable feedback/suggestion for improving the account switching feature. This could be kinda categorised as a bug so you may also go ahead and create a new bug issue on the BW Mobile github page here.
Also to note this issue only appears ,when the vaults are in a unlocked state. But if your vaults are in a locked state , it does give you the option to switch between account profiles on the lock screen itself for auto-filling purpose.