I don't think your tone is warranted and in the spirit of this community.
I don't agree with GP's fear of Apple SSO vanishing without a transition period to something else, but the general premise that this form of login is not eternal but rather short lived in the grand scheme of things is reasonable and doesn't warrant your aggressiveness.
Also you might get locked out of your Apple account for a number of reasons and will then lose access to much more than just Apple services.
It is also not really a valid argument here, given that the service we are talking about was offering Facebook and Google login options, which share the exact same issue, but with the added privacy violations of those platforms.
From what I understood from these discussions, that is not an issue with Facebook and Google logins because they reveal the true user email address, so even if they no longer exist one day, that email address could be used to recover the user accounts (using a password recovery flow through email); while Apple SSO does not reveal the true user email address, only a proxy through Apple's systems, so if it no longer exists one day, there's no way to use the email address to recover the user accounts.
Apple asks the user whether they want to reveal their email or not. If you do not receive a real email address for Sign in with Apple, it is because the user did not want to give it to you.
I don't agree with GP's fear of Apple SSO vanishing without a transition period to something else, but the general premise that this form of login is not eternal but rather short lived in the grand scheme of things is reasonable and doesn't warrant your aggressiveness.
Also you might get locked out of your Apple account for a number of reasons and will then lose access to much more than just Apple services.