That is a good point that I didn’t have on my radar until now… on the other hand, I just tested it without that permission – and in that case, Firefox should ask for it when you try to activate biometrics in the BW extension:
@crabby If it still doesn’t work, you should also have a look into this post and see if adding that file (and in some cases: also the folder) also solves your issue: MacOS Firefox bitwarden extension rejects Touch ID - #14 by Nail1684
PS: Ah, and what is your BW desktop app version?