As in, I cannot simply sign up with my own personal identifiers (email, phone, etc.) but need to participate in a google auth or FB auth mechanism ?
I found it hard to believe - is this, indeed, the case ?
It's a weird process and not particularly user friendly (passkey accounts are tied to a specific passkey and can't have additional ones added, so you need to create a new account if you, say, migrate from one hardware key to another). Hopefully they improve the process before passkey support goes out of beta.
Though I suppose there is the potential problem of identitiy collision due to public key resuse unless the keys were generated serverside to guarantee uniqueness.
Google, Microsoft, Github, Apple or your own OIDC Provider.
They do not have their own account backend.
So you dont technically need a FAANG account if you have a Gitea, Gitlab, Authentik Account or something like that.