So there would be no apple account registered on the phone.
So each app wanting to implement apple login would have to :
- pretty much implement it from scratch
- still have a very subpar experience compared to any other login mechanism (even way worse than email + password) since they would have to ask users to find their obfuscated apple email address.
Still pretty meh that it is the only solution of its kind without an sdk
Any OpenID Connect (or OAUTH2) library of the devs choice is the SDK.
The Facebook/google SDKs are simply there to add trackers and bloat.