Nice and tight with a short socket will do it, 73 lb/ft takes a lot of undoing if you have a problem out on the road. The drawbolts will prevent any chance of the wheel being pulled out of line by the force in the chain. All the bearing centres and spacer tubes butt up against each other so there is little to be gained using such force, its probably BMW over specing because no split pin is fitted. Over 10000s of miles on and off road I have never had a wheel nut come loose.
PS no split pin or R clip used to be an MOT failure if the holes and castelated nut were present.