I'm not sure I follow. I think a measurement between two fixed points is the same on the ground or in the air, and the bushing won't know the difference. It's about the bushing not "resting" in a twisted position where it spends most of its life. Of course, in motion its all over the place, its constantly changing as your tires wear, etc etc. We may be measuring with a micrometer and cutting with a battle axe.
In fact, if you just put it on the ground and do nothing to settle the suspension, the truck will be artificially high when you torque it. You probably need to drive it around a bit to get the tires out in their natural position. Of course, if you happen to own an alignment lift those fancy plates will move and help with the settling.