Not sure I personally subscribe to this, but it does make a tiny bit of sense. There are some people who claim that it isn't the holster marking your pistol, but any dirt/grit inside a dirty holster that marks the pistol. The reasoning is because kydex is softer than just about anything you put inside of it, so scratching from the kydex alone shouldn't happen. But scratching from minerals in dirt/grit could potentially happen. I suppose this makes a lot more sense if you're somewhere like Arizona or often in the real outdoors.
I'd take that with a grain of salt (see what I did there) though. Some finishes or cheap rattle can paint can and will be stripped with repeated action in/out of a clean kydex holster, but that could just be because it is just as soft as the kydex. Also, stainless steel is actually a softer metal than one would think, so there's that to consider as well.