That won't remove the erroneous new material zones. Only reloading the figure or prop from the library will do that.

I would strongly recommend renaming all of your MAT poses to MC6 files (change the file extension from .PZ2 to .MC6, and move them into a sub-folder in the "RuntimeMaterials" folder). MC6 files will not add new material groups unless you allow them to (a confirmation dialog will pop up if you apply an MC6 that contains material groups not present on the currently selected figure or prop).