To answer your question, yes.  The reason you are seeing the content distributed as such a manner is because every item of clothing and hair appearing under figures are rigged for a particular model.  The rigging permits these items to be conformed to the body for an accurate fit.  Non-rigged items will be found in their corresponding categories, either hair or props, and these particular items are smart propped or dynamic in nature.  I believe the manual describes the difference between each type of clothing and hair.

Also, the current Poser iterations may permit you to move content around to their appropriate folders but the issue arises when you want to identify conforming from dynamic.