Stumbled upon this today. Thank you, Quinn; happy to file a suggestion for this API: FB13152209.

I'm also interested in understanding if iOS, like Android, has implemented the proposed Device-bound Public Key WebAuthn extension (devicePubKey). This is described here: https://security.googleblog.com/2022/10/SecurityofPasskeysintheGooglePasswordManager.html Passkeys on Android support the proposed Device-bound Public Key WebAuthn extension (devicePubKey). If this extension is requested when creating or using passkeys on Android, relying parties will receive two signatures in the result..