magnetising the clothing is not connected to accomodating the body-shaping morphs (like bulk and body builder). V4 uses magnets on the figure in several places where earlier figures had JCMs - morphs that responded to the flexing of a body part - which were a pain for clothing makers to match. The magnetise pose makes the clothes respond to those magnets just as V4 does, so you don't get poke-through where V4's mesh is deformed and the clothing's isn't. The only user-controlled morphs that magnetising enables are a few of the breast morphs (up, down, in out etc.).