> Forced to use Safari. Forced to offer Apple Single Sign On ...

I don't understand why you think Apple couldn't make those requirements? They already do for the apps on their own store, why couldn't the require it for apps on other stores? Apple can still control the signature process to allow apps to install on devices, they can just not sign anything they don't like.

(Putting aside whether those are reasonable constraints or not, I don't necessarily agree with them, but it's a separate matter).