Fascinating thread...
It seems clear that the seller is at least being disingenuous, leaving room for a buyer to make leaps and assumptions based upon the information that is present in the listing. The name Topps does not appear in the sketch auctions, so as has been pointed out, he carefully walks the line. But it's obvious that someone could be led by the information there to think that they are official.
Adding a disclaimer to the auctions like: "These are not official Topps sketchcards, nor are they licensed by Topps." That would be what a good dealer would do, because a good salesman wants you to know what you're getting. A good salesman wants to give you what you actually want. It's a shame we've lost that ideal - and made the trade of sales such a negative thing, to so many people.
It's like pointing out all of the flaws on a piece in your listing, or glossing them over in the hopes that the buyer misses them. One is what a solid dealer does, the other, not so much.
I can't speak to some of the fraudulent activities being discussed, but this kind of stuff does risk damaging a hobby. Of course, as has been pointed out, the sketch card craze itself may not be the most healthy thing for the hobby, either. Heady stuff!