It's a bit unfortunate, because using PKI for authentication is an obvious win over sending the untrusted authentication provider your entire secret key (you know, the password). I want to use PKI. Fuck, I'd be happy just giving SSH pubkeys to every site I use and doing shit that way.
So I should love passkeys! And the spec and developer docs are cool! But they practically don't exist for me personally, and that's kind of sad.