The ABS will not kick in at super-slow speeds like that.

Dean, there is nothing so special about the VX's suspension and drivetrain that brakes operate differently on it. I don't mean to take sides against you, but you should consider the possibility that their machine is right and your brand-new rear calipers were installed with air bubbles in the brake lines and are not in fact doing much squeezing (a far more likely possibility than their machine somehow not being able to test what VX tires are doing on their load sensors).

Good luck!