What happens if some websites don't allow you to add more than one passkey? Now, you need to keep track of which site has backup key, and which site doesn't have one. Also, the website needs to store multiple public keys now.
No Webauthn support at Amazon.com whatsoever. It's mandatory SMS (you must provide a number and you can't say "I don't want this to be even a backup option") with optional TOTP.
