I think what they're saying is that for something as simple as analytics (just an example), apps need some sort of unique identifier for the user, but that the only unique identifier iOS provides is the advertising ID of the user. Of course the correct answer is to stop doing any sort of analytics, or anything else that requires a unique identifier. But the point I think the author is making is that that is a bad solution.

Of course this all ignores the possibility of creating user accounts or generating a unique identifier whenever the use installs the app, so maybe there is something more to it that I'm not understanding. Because I tend to agree with you, that developers shouldn't be doing something with user data that is prohibited.