The auctioneer knowingly keeping a secret that could cause a downturn in the market once discovered and publicized in years and in the meantime keeping a giant client sounds very rational.
Auctioneers would simply have a standard practice with respect to disclosure to protect their reputation, not keeping secrets. I know of none that advertise that they use a computer to verify the mileage/hours on equipment - if one did I am sure they would advertise it and be religious about its execution.