Probably because it has some sort of rubber padding and rubber is always in a state of disintegration giving off sulphur gas
The sulphur melts nitro finishes making a real mess
I have seen this on so many Gibsons that it is almost unfunny
I owned a Les Paul that very quickly got marks in the finish from a stand
Some shops wrap silk or dusters around the rubber bits on stands
Nitro is way overrated in many ways IMO, even though I do like it
So often you see people posting about it because they have seen others post about it in vintage vs modern guitar discussions and they just quote verbatim what others have said without their own insight & research/experimentation into it