That latter bit is a straight-up physics issue. The loading of the torsion bar doesn't really change, between either position, at rest.The difference is in the rotational forces applied to it by changing the ride angle of the lower control arm. Normally a flatter angle in relation to the ground, forces working on the suspension are closer to a right angle to the lower control arm. When cranked OR re-keyed, the lower control arm sits at a higher angle from the ground and those force arrive at a more obtuse angle to the axis of rotation, driving in towards the pivot as well as up (to a greater degree than the stock geometry). That's what generates the stiffer jouncier ride. Any method that alters that lower control arm angle will do the same. it can be masked with changing spring rates, torsion bars, shocks or tire pressures.
/I have a theory, dinosaurs are small at the front, big in the middle, and small at the back