Not true. The auction still has to have an FFL process the form 4473 and do a background check over the phone. Most of the auction houses around here seem to be FFL holders, so it's easy. Here in MI you will still be required to file the registration form if it's a handgun.
Depends on the type of auction as well, in Florida estate sales are generally exempt, as the auction company does not 'own' the firearms, the holder of the estate does so the sale is considered to be between private parties.
Last (estate) auction I went to the auctioneer specifically stated no paperwork was required.
Your state may vary.