This is really good for consumers, but I'm afraid that many websites simply won't bother to implement this. Apple just doesn't have the unique marketshare that Google and FB have. The set of users that would use such a thing is the union of privacy focused users and users with an Apple ID and not a Facebook or Google account. This set is heavily overrepresented on HN but is relatively small overall.

If I run foo dot com, is that set of users attractive enough to me that I'll spend the engineering time to implement this? I can't think of many instances where it would be.