The main reason for this method is to prevent brake rotor warpage due to unevern tightening while going through hundreds or thousands of heating and cooling cycles. Never let anyone install your wheels with an air impact wrench. Clean all dust and grit from the wheel nuts. Have an assistant push on the brakes if need be and tighten the nuts in the previously described manner and to the correct torque using a new plastic square for each nut. Avoid using an extension between the deep socket and the torque wrench if you can.
Extensions tend to absorb torque when they twist.