I believe that seller is mistaken, at best. The history of the official TSR/WOTC miniatures should go:
Minifigs (D&D and World of Greyhawk)
Grenadier (AD&D and Gamma World)
TSR (every game TSR produced at the time)
Citadel (AD&D)
Ral Partha (AD&D)
Wizards of the Coast (Chainmail and D&D)
(Minifig's "World of Greyhawk" line was mostly repackaged miniatures from the Aureola Rococo line, so Minifigs should still have the rights to reproduce many of them under their original names. For some reason, they've
rereleased the Amazons and nothing else.)
On the other hand, there were lots of miniatures companies (just like there were lots of game publishers) who advertised their products as "for D&D" without TSR's permission. That may be the case here -- hard to say without a better view of the packaging.