Okay, proposed alternate application: It is not a staff block, but a strike to the throat and groin, simultaneously (as either strike will give pause to most attackers, and if both manage to hit, it would hurt....a LOT....but that is not all, it turns into a grab. The jump and spin is to gain momentum to throw them down and out of the way behind you. The knife hand defense uses the recoil of the body landing to add controlled snap to the move, possibly suggesting it is a strike, not a block. At the very least, it is likely attacking a specific point on the next attacker's arm as he moves in. This knocks his arm out of the way so that he is open to the groin strike and rip that follows.