Practically all the methods of creating clothing for a character require an underlying body model. Doesn't matter if it's a completely artistic approach or if you use some sort of simulation (Marvelous Designer), you still need a foundation. You don't have to include this actual model, you don't need to texture it or rig it, but it will still be a great help.
Looking at the screenshots, it seems like it's a generic body, so it's probably only included in the base asset but it's not part of the runtime version.