> Does that not rather imply that, if I log in with faceid on an iphone, my login will be tied to my ability to faceid on an iphone, and hence only available on iphones and macs?
The authenticator is given a lot of leeway in how it does authentication. In the Apple platform case, it is "the user authentication on the device which is on the iCloud account and has set up iCloud Keychain".
So on my Mac I can use TouchID. On my phone I use FaceID. Both allow me to fall back to the device password (such as when I have the lid on my Mac closed).
The authenticator is given a lot of leeway in how it does authentication. In the Apple platform case, it is "the user authentication on the device which is on the iCloud account and has set up iCloud Keychain".
So on my Mac I can use TouchID. On my phone I use FaceID. Both allow me to fall back to the device password (such as when I have the lid on my Mac closed).