Genesis does have groups, and regions - you can see the groups as selectable areas when using any of the joint-manipulation tools, regions show only when using the region selection tool and allow for targeting different areas (I'm not sure how much this shows in the Genesis in DS4 .321 but we ddi see it in the projectX preview, or in the videos on the new tools, so that you could for instance select just the upper face and see only those morphs that affect the upper face). I don't know how it is handled, but it's certainly possible that weight maps are defined only across certain groups with other groups simply marked as all 0 or all 1.