Developers will not leave a choice.
Apple said it would require adding “Sign in through Apple” to all applications that support authorization through services like Facebook and Google. Developers can either add a company login system or remove all third-party options. Information about this appeared in the Apple blog for developers.
“Sign in through Apple” will be available for beta testing in the summer. It will be mandatory as an option for users in applications that support logging in through third-party services. The feature will become commercially available later this year.from Apple statement
Apple introduced its own authorization system along with the new iOS on June 3. Unlike competitors, “Sign in through Apple” will allow users to choose what information they want to share with a particular service.
For example, instead of entering e-mail during registration in the application, you can use the function “hide my email”. In this case, the system generates a random email address on the Apple server, which will send the data to the user’s real email.
As noted in 9to5Mac, hardly all developers and companies will like the approach of Apple, but they will have to update the application to support it or abandon third-party authorization services. “Sign in through Apple” is not yet possible to test, but it will probably work in one of the following beta versions of iOS 13.