What are the legal implications of passkeys? Are there any case law examples yet? My understanding is it's 100% impossible to 'prove' I know a password or not

What are the legal implications of passkeys? Are there any case law examples yet? My understanding is it's 100% impossible to 'prove' I know a password or not as it could be written on a piece of paper somewhere, and it's entirely possible for that paper to be shredded and therefore any proof of that password is gone, forever. I remember hearing you cannot be compelled to hand over a password. Biometrics et al on the other hand? Could/would a judge compel those to be disclosed? I saw a video of a police officer forcing somebody to use their face to unlock their phone to delete a video. With a password, this would be 100% impossible. So yeah, think about that BEFORE using.