If any of the iPhones are placed lens down on a flat surface the back of the phone at the lens is raised up a bit because of the protruding lens. The contact part on the lens hitting the surface is it's very edge, not the lens itself. So the part of the lens that the camera sensor sees through never touches a flat surface- that's why there's no scratches on iPhone lenses (for the most part).
I’m surprised the people in the other thread complaining about screen scratching haven’t busted down the door to this thread and started yelling, “yyeeaaaah the whole f’ing phone is scratch prone!!! Aaarrrggghhhh!”