They must remove all bids from the fake bidder, not just on the domains they won and didn't pay for. This bidder's participation caused other investors to overpay on every domain auction they bid on, even the ones they lost.
Two or more bidders run a domain up, and block any legitimate bidders from bidding. Then the top bidder doesn't pay, leaving the second bidder to get the domain at a major discount after all the winner's bids are removed.
This is the scheme that has lead to many GoDaddy auction rollbacks. Michael N@NameBio has covered this scheme extensively.