This was addressed in the article. If the service provider does not have your email address, they are severely hampered with regards to customer support.
No, they're not. They're just relying on email as a user verification methods as it's the easiest approach. Other methods are possible.
Did you read the article? It seemed very clear to me that they had significant issues with customer support past just verification.
And what would you suggest as an alternative way to identify the user, anyway? Any alternative method of authentication seems doomed to fail - using a real name runs into issues with duplication, requiring users to set a username would likely require significant changes to the platform to support it and lots of people would forget it when they couldn't get their preferred username, and having a customer support code inside the app wouldn't help when the user loses access to their account.
It seems like there are alternatives, but none that the average user who signs in with Apple and needs to contact support will be able to get past on a consistent basis.
I actually think the customer experience of "I switched from apple to android and now I dont know any of my usernames" is a bigger issue. If apple wants Sign in with Apple to work, it needs to behave a bit more like an agnostic 3rd party password manager, work on every platform, and have ways to interact with it on any device. They should release Keychain as an Android app and Chrome extension, and allow you to use it to see your Sign in with Apple data.
If I can't contact my customers, how do I support them (e.g. report a security problem)? If my customers can't communicate which account is theirs, how do we help solve problems? Email addresses and/or phone numbers make this a lot easier.
I never want "communication" from an app developer unless I initiate it.
It's a fair point, and perhaps its one that the likes of Apple SignIn should solve. On the one hand, even Microsoft and Apple send me heaps of spam under the guise of "communication" and I don't want them to have my email address if I can avoid it. The OP says they have trouble with support, but they can (and it sounds like do) tell people to just check their Apple email. Most places that I contact for support require me to put in a contact email for that ticket because people use throw-aways anyway. As for security problems, well I'm glad you're one of the few companies to actually disclose security breaches. But if the information on the website is actually sensitive, then there should be additional checks to begin with. If it's CC info, you should contact the CC company, there should be 2FA, there should be more than an SSO service, which already prevents the biggest and worst security breach of leaked passwords. In short, I doubt the need to contact a customer unsolicited is so great, common, or difficult as to require that a user disclose a non-obfuscated email address, which people already commonly have throwaways for. And the reason they have throwaway accounts is because 99% of the time, when I give someone a ...@spamgourmet account or whatever, that address gets spammed, even though I told them not to put them on the mailing list (because they share the email with third parties, or just plain ignore it).
The tradeoff is a bad one. I do not have sensitive information on Reddit that is not public. A private investigator could probably deduce who I am by looking at my Reddit posts, figuring out where I live, where I went to school, what family members I have, what my job is. They don't need to contact me urgently about a security breach. You can say when I sign on and lock my account until I acknowledge it, but it's not urgent. Even a website that might need sensitive information and, for some reason, doesn't want to require I actually verify my identity for real to upload that sensitive information, that doesn't mean I'm using the website in that capacity and should give up identifying information in case I need to give up identifying information later and you need to contact me that my information has been leaked.
The perspective is worth thinking about, but I'm unmoved that it amounts to pushing the needle to "you need my real, primary email address." I believe the tiny, tiny minority of companies that actually need that and shouldn't just rejigger their system to better security and privacy practices to start with can find reasonable workarounds or resort to mild inconveniences like requiring a callback number on support.