Google should just add a similar requirement in response. With this rule Apple is forcing their signup method to be taken up across all platforms (web, Android, iOS) because you can't only enable logging in with Apple on one platform.

If Google were to implement the same requirement, any cross platform app with Apple's login would also now have a Log in with Google button, making sure that Apple won't be getting any Oauth monopoly any time soon just to keep them in check.