Solved by ptrblck in post #4 
              
              
                No, that’s not the case and is the difference between the 2D and 3D layers. 
While the 2D layers apply the kernel on the H and W dimension for an input of [N, C, H, W], 3D layers will use a 3D kernel applied on D, H, W for an input of [N, C, D, H, W].