Interesting photo comparison. While I guess it's better to have the steering arm parallel to the lower arm, one can see it's considerably shorter than it from the picture of the car with Spax suspension where the inner joint is angled.
However, it's nearer the upper arm and I imagine this is shorter than the lower one in any event. Moving the ball joint up would reduce the bump steer in that case. I would though wonder whether a spacer would create a weak point.
The other point is, what is (or are) the spring rates? A car with a stiffer front will exhibit less bump steer, even with identical suspension design.
