Perhaps I didn’t explain my idea well in my post.
Currently (from what I can tell) there is no option to use biometrics (FaceID in my case) to unlock the app only for a specific amount of time.
If I enable FaceID, I can use my face to unlock the app no matter what. Wait for hours, restart my phone, makes no difference.
What I would like is to have a new option to require the master password after a period of inactivity. As a former 1Password user, this is a feature I really do miss.