HUO means almost nothing IMO. It's an adjective people use to suggest the condition is excellent. But there is simply NO way anyone can guarantee a game is HUO even if they have the receipt. The game could still have been taken to a show for a day or two (which would negate "HUO" in many people's opinions) and you would never know.
Take "HUO" with a grain of salt and don't put too much stock in it.