I liken that statement to "We took a knife and cut the Mona Lisa out of its frame to insure that it was indeed the frame that it originally came with - that's why we list it as new..."
I'm still trying to grasp the logic behind the act. You want to insure something is still wrapped as new - by CUTTING OPEN THE BOX SEAL? I would think the seal alone would be proof enough! I'll grant you, there are places online where you can purchase used tax stamps and put them on just about anything, but still...
If anything, that makes me more suspicious about the sale, not less suspicious. Didn't the older decks have wax seals on the vellum and not something that looks like a sticker? And is it my imagination, or is that sticker on the vellum not even covering the open edge of the vellum? Meaning that anyone could have taken old vellum and wrapped it around those cards.
Maybe it's genuine, maybe it isn't. I wouldn't trust it, personally.
Do you have the link for this sale?