The easiest way to explain it to you:  push pull steering under hard braking the axle can rotate just like the rotation that occurs in the rear under hard acceleration. It will bump steer since you are holding the steering wheel and not allowing it to push the drag link, this will cause the vehicle to turn since the only thing that has give is the wheels. This is why you need something there to stop the rotation, even though it may not rotate a lot it can kick you almost sideways when you try to over correct the bump steer. This is the main reason you don't need it once you convert to an IFS box, no more drag link bump steer.