A way to think about it is that iOS 7 gets closer to real world interaction. You don't press a button to sit in your chair, you just sit on it because you know how to do it.
A microwave oven might be a better example, since a chair is inert.
On a microwave one has to have discoverable controls. Imagine if everything was just flat with the fascia, looking no different in presentation to the maker's logo.
It might say 'Cooking power: 80%' with no indication of how to adjust. Apparently, though, if you press on the word 'power' repeatedly you can change it!
I don't think we'd accept that.
You explanation is just the contrary, you press the + button because you have tried to push it without knowing what will do.