Obviously they're promoting the phones that need promoting. AT&T wants to sell ALL their phones, naturally. They don't need a promotion to sell iPhones. So they pump up the others because they don't want stock sitting on their shelves.
When Apple creates a stupid policy like this, it's like pulling teeth to get around it, even if all the Apple reps know it's a stupid policy. It just takes so much time and energy to get to some one who can actually do anything about it.