I think we are talking about 2 things. I'm not saying to export a figure in default pose out of poser (to reimport as a spawn)  but as a posed object. It comes back as a single object so, no seams.

I,m getting myself into a corner where I'll have to prove my point. I do this with Zbrush. You sculpt the posed object,, import the uvs, reimport into Poser.,, load a material group in matroom... render.

The morph brush should do the same on a single object,, in theory.