I’m admittedly and probably splitting hairs, but that’s not totally true. The load on or off the front suspension will be directly and inversely related to the load on the rear suspension. If the rear suspension is not loaded as it would be with the car static on the ground, the pinion will not be at the same angle as it will be with the suspension in the static loaded position. This difference may be very slight, but if you’re going to set pinion angle, especially in a race car, you might as well be as accurate as possible.