Take house auctions: it always says 'for sale by auction, unless sold beforehand' or some such like.
But not once the auction is under way. It only applies while it is in the auction listing *before* the auction starts. With eBay, the auction starts the moment you list it and your legally binding contract starts then.
As I've said before, I fully understand the other side of the arguement, so I'm not having a go at anyone. Just posting my point of view.