[jiggawatts]

That's not what I mean by "sync". If I don't have the phone with me, I can't authenticate.

Also, I use Firefox exclusively.

This is precisely what I mean: common scenarios are not yet supported.

[sbuk]

You’re somewhat missing the point of what passkeys are. Instead of the something you know part, i.e. a password, the authentication is done by something you have. Your common use case is only common to single factor password authentication. It’s not a situation that is allowed for in passkey’s security model.