Multiple uv maps for single figures is very common. The whole idea is to put larger uv detail mapping where it's needed, and to decrease UV area that don't require as much detail. I've seen it in other apps as well as poser/DS.

You can easily shuffle around uv maps in uv edit pro, but when you are actually working on displacement or bumps maps on the figure, you end up wth the problem they were trying to solve.. not enough uv mapping detail where you want it (of the head), and too much on areas that don't need it.

It's just their solution to the problem.. I've seen many.

Way too many people take way too many things way too seriously.