Well yeah there's that, but it can't have been just one person; there's at least dozens of people involved in the trading and maintenance of these things, there's paper trails for the purchase and I presume installing and replacing of the odometers; there's bound to be loads of people that are in the know, and since the true odometer reading can be read from the onboard computer, I find it really hard to believe that nobody caught this before.
It would've taken just one case of a mismatch between the digital and physical odometer without it being mentioned for a huge stink to be thrown up. And it'd also be the auction house's name on the block, because they should check these things themselves. If this is as widespread as they claim it to be, then even the occasional spot checks would show it.