thank you. You are right, Webauthn taps into SDKs of platforms like iOS, Windows Hello, google's version of android. They use infra-red depth perception sensors to create a mesh of the user's face as ID and store it on the device's secure enclave. It can only be accessed and used on that device. For that reason, Apple users have to set up fingerprints separately on iPhones and Macs. The same will be for FaceIDs on the new-gen of Macs - users will be setting it up separately on different devices. We instead store biometrics in the cloud so it is not tied to a specific device.