I think I understand the GP.

Let's say I sign up for an online game using Apple's secure sign in because I don't want to share my information.

Some time passes, and I've invested 250 hours into the game, when Apple decides to ban my account for whatever reason (perhaps I've refunded too many apps, maybe the credit card that pays my Apple Music expires, my country gets sanctioned by the US gov. etc.)

Apple would, presumably, shut down email services for me. Meaning, I won't be able to log into that game any longer. With no alternative log in method (which would defeat the purpose of using Apple's sign in) I would likely lose access to that game forever.

Isn’t this just a general SSO problem - I assume the same would happen if someone signs on with Google/Facebook/Twitter and is banned from one of those services?

Is the idea here that there’s a higher chance of this account type being banned without recourse because of the number and type of ecosystem interaction points (App Store, subscription services, etc.)?

Unlike Google, where high-profile Twitter shaming is basically the only effective technique for resolving issues, for consumers the Apple stores are a legitimate place to go and complain.

It’s not perfect but on the spectrum of bureaucratic chaos, Apple is a lesser offender.

In all those cases you are barred from logging in, sure, but the service still has your email address so the account is still "yours".

You can choose to share your email with each developer or not, so if you feel particularly attached to a service you can disable the email obfuscation. Or sign up withouth Apple ID if you know beforehand.

If Apple decided you're a bot and deletes your account, everything tied to it will also go.

This is true for Google, Facebook, and Twitter logins as well. It's a valid criticism for using any third party authentication provider (which I personally avoid and will be avoiding Apple's).

The login provider doesn't store the service account itself, so it's possible to "eject" your account and use some other sign in mechanism as long as you have control over the email address.