Then maybe you should re-read it.. let me break it down for you.
People have put the iPhone into their pockets with nothing else in there (I.E. Keys) and its been scratching. From what I've heard something as small as a grain of sand in your pocket can scratch it, while people going over the screen with a razor can't. There have been several posts about it on this forum.
https://forums.macrumors.com/posts/4409516/
Now do you understand or do I need to break it down more?