That is surprising (since it is Chromium-based), and maybe reportable as a GitHub issue. Vivaldi does seem to be in the minority, though, as generator settings are preserved in Chrome, Firefox, and Edge (as tested by @Neuron5569 and me above). Are any of your other preferences lost on logout (other than the PIN), such as the vault timeout settings?
Another test to do (I may do it myself if you don’t) is to check whether having a second logged-in account (using the account switcher) makes a difference in the behavior. In my experience, the vault cache for all logged in accounts are contained within the same file, so perhaps more data are preserved on logout of an account if there is also a need to preserve cached data stored for a second account .
I assume that you are not implying that you were expecting your settings to survive the uninstall/reinstall, but rather that the loss of generator settings on logout persisted after a reinstall (?).
FYI, I also performed some tests in Edge, and can confirm:
The generator settings (but no other preferences) are lost when logging out.
The loss of generator settings on logout occurs whether there is a second account logged in in the account switcher or not.
2024.12.4 → Generator settings preserved on logout.
To which I can add:
2024.11.2 → Generator settings preserved on logout.
Thus, this does have the hallmarks of a bug/regression.
For the record, in my tests with Chrome (in which the generator settings are preserved), the extension version is 2025.5.0 — thus, there is definitely some browser-specific problem in extension version 2025.5.0.
(all on Win 11, latests updates, and all on extension versions 2025.5.0)
(I could also test on Chrome and Edge, if you want to, but I think it’s already clear, that as I wrote before, it’s not only the extension/browser combination alone…)
that need a cleaning! 
