I’m highly skeptical of Passkeys/Webauthn as it would seem to not have the same legal protections that a password has in the US. Maybe this is me becoming a conspiracy theorist.
The current legal climate is mixed but we have court cases that claim biometrics are not covered by the 4th and 5th. We also have the opposite. The reasoning being that producing biometrics is not testimonial. Until decided by the Supreme Court, I'll assume that anything that can be produced without my mind is not covered and that includes this.
I am not a lawyer and this is not legal advice.