Back in the days of Poser 4, users discovered the hack of mat poses and mor poses. 

Before mat poses, you had to manually apply textures to each and every surface.  To apply morphs, was more complicated.

Eventually, the hack became a standard.  Once Poser 6 introduced the mc6 or material collection that will apply a collection of material settings all at once in the material room, Poser vendors began to use them.  However, since DS cannot read the mc6, vendors who want to sell to DS users create mat poses.