[j45]

Appreciate this - I can't say it makes sense because some third auth might be specifically selected for user-type or industry alignment (LinkedIn, Github, Microsoft login, etc).

M365 login specifically can hook into quite a bit of organization information along with the user itself that can help configure apps, wouldn't be relevant for Apple in those kinds of B2B scenarios.

Apple ID is almost always a personal or individual one.

It can be convenient for sure, makes me think about how there's other things where Apple is/was the only choice for the most part like payments, although that's changed for the time being.