I doubt it is the stampers. But maybe. They are probably using the stampers from the black vinyl run, and they may have picked up some abrasion in transit/handling.
It sounds more like process. It could be in their automation, in sleeving the discs.
But I have to say, I rarely have a problem. I suspect GZ use a formulation for their mold release compound. Colored vinyl is always problematic.
Use Nitty Gritty FirstRV as a pre-cleaner. That has solved just about every issue of this type I have had. It even got an original De-Loused to play reasonably quiet - which was near-impossible.
My rule of thumb on vinyl - if it looks good, it is good. Just need to find the right products and techniques to make it sound as good as it looks.