fid02
When I attempt to create a passkey with Proton Pass with Google Play services installed but without being signed in, I get the following message: "Sign into your Google Account to create passkeys\nTo create passkeys, make sure you're signed into your Google Account." This indicates that it is necessary to sign in. Is am not attempting to use Google's password manager. I even have it disabled in the Passwords & accounts settings. The only deviation from the instructions was using "Enabled for 3rd party passkeys" in the web-authentication-android-credential-management flag.
Google indeed has the option to not collect login details when using FIDO credential if Google Play Store and Google Services Framework have network permissions, but there is no reason to believe Google doesn't at least collect the relying party and any non private key information. At least U2F with hardware keys doesn't require giving Google the option to collect the information (unless Vanadium sends the information to Google, but I trust that far more than a Google black box).