This is a renderer bug, not a plug-in bug. Assigning an emitter to each face of a mesh should produce the same effect as assigning that emitter to the mesh as a whole, but it doesn't.
When multimaterials are used, Max gives the plug-in per-polygon material assignments and the plug-in sends the data as such to the renderer. Until the renderer bug is fixed, we'll try to work around it by checking if the per-polygon data actually references more than one material; if not, we'll send the material per-mesh. This will solve the case you showed in the other thread, but it won't fix scenarios where a mesh actually uses two materials, one of them being an emitter.