It certainly did make a big difference. It worked by eliminating the short-period "chatter" in the suspension travel (actually, most likely the undamped movement in the tyre wall) and kept the body of the car (and hence the wings) at a much more constant height above the road surface. That improved both suspension control and the efficacy of the wings, improving cornering performance. Renault argued that its role was principally related to the suspension dynamics, the FIA disagreed and "decided" that the primary action was aerodynamic.
I never really understood that ruling, as surely the whole of the job of the suspension is to keep the car off the road. If you are going to argue that well-controlled suspension travel is primarily an aerodynamic feature the surely you need to be running fixed wheels and solid tyres. Yet another bizarre and illogical ruling from the FIA, but hey, we're used to that.