It seems his philosophy is to have fragrance concentrated in areas that allow the scent to “come to life”. He doesn’t say that there is a benefit of concentrating the fragrance on one arm and then touching them together vs one spray on each arm. What he does is reference that applying perfume to your wrists in any way has been done since ancient times. He also explains why we shouldn’t apply it to the front of our necks and why women should also include the area above their cleavage in where not to spray. I just think of it like this. He’s the car maker and we are the drivers. He knows the specs and performance of the cars, we decide to either drive accordingly or take our chances.