Of course. But the "Sign in with Facebook" button didn't appear by magic on the Android app, did it? Someone had to add support to their app for it.
This change may incur similar cost, as Apple are forcing Sign in with Apple on _any_ app submitted to the appstore with third party login support, which is a crazy number of apps. You have a "Sign in with Facebook" button on your iOS app today? Guess what, you have to add a "Sign in with Apple" button or you don't get to play on Apple's store.
Many of these apps also ship on Android, and users will rightly expect the account they created on one device to work on another.
This change may incur similar cost, as Apple are forcing Sign in with Apple on _any_ app submitted to the appstore with third party login support, which is a crazy number of apps. You have a "Sign in with Facebook" button on your iOS app today? Guess what, you have to add a "Sign in with Apple" button or you don't get to play on Apple's store.
Many of these apps also ship on Android, and users will rightly expect the account they created on one device to work on another.