The won't reduce wheelspin.
I can see them reducing wheelhop, but at the expense of full articulation. They claim that they don't "bind" but that can't be entirely true since they don't move through motion arcs that are identical to the arcs of the stock arms alone...
More than anything, they reduce fore and aft movement of the the control arms (movement that is allowed by the "play" in the stock rubber lower control arm bushings).