Refresher, for those curious. This is a follow up from his previous vid:
The lens does not scratch with a razor blade, meaning it's not going to scratch with keys in your pocket, or most normal objects people carry around with them that the lens might come in contact with.
It only scratches when a Mohs 6 or greater hardness is used against it (same goes for the Home button). Also if you notice, the point and area at which the lens scratches in Jerry's original vid is when he's applying the most pressure to it with Mohs 6, i.e. really digging into the lens.
Point is, the lens isn't going to scratch under normal scenarios when coming into contact with most objects.