Isn’t Single Sign On monopolistic by definition? Do we want 400 SSO providers? Wouldn’t that not be “Single” Sign On? Before we ring the alarm of anti-trust and monopolies, do we really understand what the alternative means?
I've not read any of the apple docs so I'm not sure but I suspect Sign In with Apple is going to be required as an option, not required to be used. In other words a given app may have Facebook, Google, Apple sign in.
I don't think it's required today but what if Google takes the same stance as Apple and mandates that all Play Store apps must have Google sign in available.
So not 400 but at least two and likely three since Facebook is popular too.
If Apple mandates the use of Sign In then I think there may be some monopolistic issues. I'm not familiar with the actual law, grossly generalizing some comments below the theme is Apple cannot be monopolistic since there is an alternative in Android and Android has a larger world wide market share. I don't understand that line of reasoning but admit I do not know what the law says. Seems to me if you have complete control and it's harmful than that is monopolistic...
In the long run, there will probably be government-provided digital identities for everyone.
But right now, Apple is probably one of very few institutions that are both willing and able to provide a SSO system with great usability, privacy and market penetration.