The prices they got last quarter for raw, 'buyer inspect/all sales final' GA books were absolutely zany (to the point where Filter among others wondered aloud why he even bothered to slab and sell books through the usual auction houses). So they do have a good recent track record. That said, agreed, it's the last venue I'd use for an Action #7 of all books.
Weiss's auction house has been auctioning collectibles and comics for 3 decades. Longer than any of the other auction houses.
They've probably got a pretty deep following of buyers and the prices they fetch seem to be decent.