X/wind
I believe that the wing down should not be flown on the approach but only applied during the hold off to the landing.
With regard to teaching the crab and kick straight for the touch it should be taught and practiced first for the following reasons;
A) Not all aircraft will allow the wing down method or at least are limited; long wingspan, short undercarriage, engine nacelle ground contact. Propellor ground clearance (many light twins). On some types the aileron will loose effect before the rudder during the hold off making it impossible to maintain the wing down.
B) The crab and kick straight method is always applicable either wholely or in part but is harder for the student to grasp and therefore should be taught early and be in the pilots armoury from the outset. The wing down when it is appropiate is very effective i agree but it can be taught very quickly at a later stage of training or during a subsequent type conversion.
C) A low hour student or PPL can become easily confused and lower the downwind wing with catostraphic results. We read of these accidents month by month.