Liabiilty!
If they sell you a RTR hy-rail, and you do something stupid, they could get sued BIG-TIME.
Instead, they sold you a truck with "inoperable residue parts not removed" and what you do with it is your problem.
If you buy a hy-rail from any railway, they will generally make it no worky. UP simply removes one wheel from the stuff they sell.
BTW, what did you pay for it (ballpark)? I'm looking for a hy-rail to run on NARCOA trips. I REALLY would like to find a set of the rail tires for a jeep, but no luck.