Get xfile subset with mesh editor

given an xfile with a number of subsets, if you do a getslice(Node) to get only one of them and send it over to a shader for drawing all is good but if you get the same slice and separate the vertices and recompose them back, then all subset appears, this is weird.

wow 2007

and more recently but no answer

just uv map and prepass with layout on uv

I ve found out that the xfile plugin in blender has a nice option to eport only selected objects which resolves my issue, still I think it is a weird behavior, isn t it?