And therefore comes the answer: It is true that AV exists in each one (in the fourfold form of the simple, unfilled Havayah in each case), and it is indeed the truth that in the case of AV, SaG and MaH, the fourfold form is not taken into account in the operation whereby they reach 72 in their expanded form, signifying their connection with Arich Anpin (the overall AV). The reason why we do not take the fourfold form into account in the case of AV, SaG and MaH is that they each have another AV particular to their individual function besides the AV that exists in all of them by virtue of their simple form.
BaN, on the other hand, does not have any other AV (i.e. one particular to itself through its filling or expansion), and therefore shows its relation with Arich Anpin (the overall AV) through the AV contained in its fourfold form.