Except in cases where the non-legit bidder or the underbidder snipe. In that case, someone may have clicked to place a bid, then gone to enter it, only to be informed they needed to enter a higher amount base on someone having entered a new bid since they clicked on "place bid." They get a message saying "the following must be corrected before continuing."
So let's say it's the last minute, and I go to place a bid. I enter the amount. Meanwhile, you enter a new bid higher than mine, but you're not the high bidder, because a shill has outbid you. I click "submit" and am told I need to enter a higher amount. My bid doesn't register; yours does, though you're not the high bidder. Take out the shill's bid, and the next highest official, registered bid would go to "Bill," who bid less than I was willing to bid. My bid would have registered if the shill hadn't bid. If the seller accepts your offer of one increment over what that Bill bid, he loses money, as sans shill, my bid would have been second-highest, not Bill's.