Are you sure that the cover is not laminated or coated? I've had a few of the softcovers and never came across one that was too glossy. Maybe you could provide some photos so we could see what you are indicating? It would be good to see the cover edges. If it was laminated they are often wrapped around the cover, so that type of laminate would be obvious.
You know what - you're absolutely right! I thought I'd looked at that but apparently not. It's definitely laminated. So you can ignore that
Foul.
I have one more bit of info now that I've started reading it.
On the Explanatory Notes page, the first print refers to the Dungeon Master's Handbook, whereas later ones refer to the Dungeon Master's Guide. Not sure when the switch happened.
On the whole it's quite odd that the product page in the first print refers to it as the Referee's Guide.