I think there's something inherently unethical about Apple making it against the rules to let people know they're paying more to buy it on Apple though.
That’s like Apple selling their watches in a Target store and on their box advertise lower priced wrist bands on apple.com on the box. No way would Target tolerate that.
I think it's more like Target dictating what marketing materials may not appear inside the box, because this happens after you already have the app.