While I'm not happy with the supplier, I don't think this was intentional on their part either. They just source AC adapters from someone else in Shenzhen. You can imagine they aren't real familiar with the consequences of trademark infringement. Which is what this was.
Edit: Note that it was all auctioned off later without the adapters. So the concept is known to them.
Also, see my friend's experience of a CD-ROM with a fake "Compact Disc" mark that resulted in a shipment of SBC's getting seized. Perhaps that one is more clear where the receiver wouldn't have any idea to even ask: https://news.ycombinator.com/item?id=24469959
I will also hazard a guess that many HN folks have ordered things like generic arduinos, led blinky stuff, etc, and gotten an adapter with a fake UL mark. Smaller scale, but the same thing nonetheless.
So you were their first U.S. customer and they'd never shipped anything to the U.S. before?
I think I was just shipping during some customs frenzy to actually do something about it.