It looks like a great solution to attest I have a FIDO key without exposing who I am. But how do they know I'm a human? Because I have a FIDO key? Seems like on

It looks like a great solution to attest I have a FIDO key without exposing who I am. But how do they know I'm a human? Because I have a FIDO key? Seems like one human can buy many keys.