That 2" is added between the spindle and the lower ball joint, which is also the outer tie rod attachment point.
So, another way to think about it is that you lowered your outer tie rod end by 2" with regard to the steering axis. Which is where the bump steer comes from, the angle of the tie rods is changed significantly. Because the tie rods are not parallel to the UCA's and LCA's, you end up with more toe change throughout the suspension travel than with OE spindles.
It also effectively raises the roll center of the car, because of the change in the UCA and LCA angle. That's for a given height though, ie, comparing the roll center with the car at the same ride height lowered with the torsion bars vs. lowered with the drop spindles.