Unable to sign in to a Google account using a saved passkey

I played a bit around in google -it seems google is using the passkey as 2nd factor after keying in User/Password. Instead of OTP it grabs the passkey. If you log off google it might keep in a cookie to suppress any 2nd step auth at all after once successful login (especially when you said in login 2nd factor step "don't ask me again") - if you do in private mode or wipe cookies it forces the 2nd factor - I could not find a way to use passkey as main login mechanism. It seems that's just a 2nd factor, but always user/password is mandatory in first step. Similar like you do for 1password.com login - either OTP or passkey