I think it can be the actual headset cup that makes contact with the steerer or the very edge of the bearing or something.
IMO it’s a pretty fatal flaw in King headsets and it’s very telling that they defended their decision not to pay the licence fee to use the wedge system by saying their design was better yet changed to a wedge design as soon as the licence ran out.
It seems like it’s a known problem (especially among mechanics, show any decent mech that steerer and they’ll know you’ve used a King headset) but for some reason no one wants to call CK out on it. Like CK stuff holds such reverence that folk don’t want to talk ill of it.
All I know for certain is that I’ve personally never come across that kind of steerer damage that was caused by anything other than a King headset.
I do have a King headset on one of my bikes (it was in a bundle of stuff I bought which included the fork with the damage that I mentioned in my last post) but I threw away the CK scuff washer and top cover and run it with a wedge and top cover off an £8 eBay fake.
I don’t think the structural integrity of your fork will be affected really. Afaik the damage happens via wear and not compression so the damage you see on the surface should be the extent of it if you know what I mean.