It's only unique in name!
It's just a separate layer of polys with it's own mapping. It's easy to modify as Wendy says.
You can modify DAZ or other clothing the exact same way, as long as there is body under it where you cut it with opacity. In fact, the skin layer can also be treated as such, so you could put bones inside it and have opacity on the skin layer(s) for open wounds and such.
Clonecloth is just an RL name for the same type of clothing you would be creating in any other software.