I can't help you with the exact technical details, but AFAIK a SubD'd Genesis can't be morphed directly. Neither in Studio nor Poser.

I asked this over at DAZ once it was clear that Genesis was basically a low res cage because I was afraid to loose a lot of sculpted mesh detail I had created for my own figures.

Which is exactly what happened.

You can morph the low res Genesis cage, but the SubD'd high res mesh is just a virtual algorithm created during rendering.

It can be frozen and exported, it could even be used to build a separate high res Genesis figure, but it can't be directly manipulated to create more detailed new shapes.

The Genesis topology is quite efficient for such a low res mesh, I give DAZ that.

But if one wants the same level of detail as with the older high res meshes, then currently displacement maps are the only way.