Apple's not rejecting apps that track their users, it's rejecting apps that don't use Apple's user-tracking system.
Also, what Apple was trying to combat was persistent tracking without user knowledge (done originally using iOS's exposure of device ID, which was deprecated, and now with these "cookie" tracking implementations). Allowing a user to initiate sign in to an app is a far, far cry from that (and it would be preposterous for iOS to disable the ability to log in to apps).
Also, what Apple was trying to combat was persistent tracking without user knowledge (done originally using iOS's exposure of device ID, which was deprecated, and now with these "cookie" tracking implementations). Allowing a user to initiate sign in to an app is a far, far cry from that (and it would be preposterous for iOS to disable the ability to log in to apps).