Developers can in turn allow those user accounts to log in but only enable some features unless a real email is used.

Sure, Apple could add even more complexity to their review process (delaying approval), or give stiff penalties to developers for working around it.

Apple's recourse to remedy a situation where a developer does not want to allow Apple to forcefully insert itself as a middle-man is primarily punitive.

Thus, as stated, this is mildly to very developer hostile.