I really don't see a problem with it. Apple's default UI is not great, and it can be highly confusing if the user doesn't know why the app is suddenly asking for access to their location or photos or whatever. By explaining and asking first, you smooth that over. There's no deception or trickery, it's just a matter of not surprising users.

(And to be clear, I've never built one of these extra permission prompts, so I'm saying this purely from the perspective of a user.)

It's not a grey area, it's a dark pattern, and you're basically intentionally breaking Apple's app policies, and screwing your users over just to get more permissions than you would get if you followed the rules.

Fuck you.