I tried what you said above, but same result.

Just to check, I imported the original OBJ into Blender, and it imported into 2 seperate pieces....abdomen and chest (with vertice counts of 1826 and 2416, respectively).

When I exported the cloth room modified OBJ from poser, and selected the "As Morph Target..." and "Include Existing Groups...", I get the same output as the original (i.e. imported into Blender, 2 part, same vertex count)

Sooo...I have no idea what that means, but trying to give more info here!