I will not go into details, let's say the game uses similar structures to current 3d softwares, that is vertices, faces, vertex groups and bones(or joints, whatever you name them). Each vertex can be connect to up to two joints, and the final position of the transformed vertex is decided by interpolating using the weights of the two. The only big difference is, the game uses two position values for those vertices that are connected to two joints.
The logic is like this (V = finaly vertex position, Vo = original vertex position):
V = Transform1(Vo1)*Weight1 + Transform2(Vo2)*(1-Weight1)
But in other 3d softwares, it is like this:
V = Transform1(Vo)*Weight1 + Transform2(Vo)*(1-Weight1)
So if I understand correctly, if there's only one Vo, it is not possible to calculate Vo1 and Vo2, or do I need extra informations to do that?