It doesn't look like the seller drew attention to the collectible details. In typical ebay-ese, '1st-print' is misused to mean just about everything. Someone gets a mid-80s orange spine
DMG, learns it's for '1st edition,' & next thing you know it's listed as: "1st Print Dungeonmaster Guide Warhammer Runequest Dicebag LOOK!!!"
TSR's own terminology does little to clarify things. I have a
DMG that was printed within a month or so of this one [mine has white flyleaves & no trailing D], but is not directly identified on the title page as a different printing. Providing a link to Acaeum's exhaustive history of printings would have been the only way for the seller to document it's significance.