If I understand correctly, V3-to-V2 has a recut mesh (and joint setup) which allows her to wear existing V2 clothing. Since this would alter the vertex count on each group, the regular V3 body morphs shouldn't work on V3-to-V2.

Think of V3-to-V2 as being the new equivalent of Victoria 2 P4. V1/V2 body morphs weren't compatible with that recut mesh, either.

Of course, since I don't actually have Victoria 3 yet, I could well be talking out of my arse.