V4 uses a set of hidden magents parented to the figure to adjust the mesh as you pose - they largely replace JCMs for fixing deformations and adjusting the breasts in response to collar movements (and they also have visible controls to implement the movement morphs on the breasts). The magnetise poses tell Poser to apply the magnets to the clothing as well. The advantage of this is that people making clothes don't have to make matching JCMs, so you don't have to worry about keeping the collars locked in place or manually zeroing the morphs when the maker doesn't include the moprhs.