Earlier quoted context omitted.
> 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.
> No, they're not. 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 change…
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.