I'm not sure if Holden recommend Superlift shocks as their WDH doesn't have height adjustment provision? I think if you have a WDH such that towball height is correct, or if you have a height adjustable WDH that there is no need for the lift shocks.
I can confirm that the only difference is the inclustion of the WD hitch for the 2100KG pack. You get two tow ball mounts. One for the standard duty towing and one specifically for the WD hitch. When I ordered my Calais, I got them to include the GM hitch cover which makes it look nice and neat when I don't have either of the towbars in.
I think what is meant, use normal tongue/towball for normal towing, and if you optioned Load Distribution Hitch take remove the standard tongue/towball from the towbar receiver and insert the Load Distribution Hitch when towing heavy loads e.g. over 1600kg (although handbook recommends when towing over 1200kg)
