Tsuande is currently cut into two pieces so her chakra system around her body is destroyed and disrupted yet she could still summon Katsuyu. Therefore, Neji's inital attacks of him cutting off the initial tenketsu will not be of harm as she can still use chakra hence deliver a killer blow. This would be true for the initial cutting off of the tenketsu. Also if Tsunade pucnhes the ground, Neji will not be able to do the Hyuuga gesture before his moves as there will be a uneven ground.