I finally reviewed the process to convert Genesis 8 Clothing to Poser and imported into P12 the sweatshirt combination as conforming clothing.  Below is the image of G8F with the outfit in a Poser 12 environment.  The clothing moves with G8F mostly with poke-throughs in extreme poses.  That doesn't surprise me.

Without knowing exactly how the outfit was generated for Poser, I will need to outline the process of how to prepare the clothing for export and then import it into Poser.  The original outfit is already rigged in TriAx Weight so in DS load the 2 pieces into the scene and make sure that both pieces show up as separate items in the hierarchy.   Save each piece as a Scene Subset in a temporary location.  These will be your DUF files.  Next, create the Poser Companion Files and designate the Poser runtime folder you wish to save as a CR2 figure.  In P11, navigate to the folder you exported the outfit to and load it into the scene.  Select each piece and save it back into the Library, generating a new OBJ when the window pops up.  Open P12 and load your G8F and conform the outfit to the figure.  

I didn't encounter any problems throughout this process and the only issue I can imagine with the OP is that both a figure and a prop may have been generated when creating the Poser Companion Files.