It is illegal not to report the odometer misreading in a sale. The real question is, who make the odometer change and where did the intentional or not breakdown happen on failure to report the odometer inaccuracy.
Better stated, I think, as who knew the odometers were changed out to zero reads, before the vehicles were then driven another ~200k miles.
Trying to craft a scenario where no one at FedEx had any knowledge at all that their well used vehicles suddenly had zero miles seems like low-return effort.
For an even better question, why undertake that specific project (at scale) except to perpetrate fraud?