The bug description is talking about LOD1 re-import. But the general behaviour is still buggy. I can reproducibly import skeletal meshes with LOD0 having the problem of the skeletal mesh editor showing only used materials while dropped in the scene, it shows all referenced materials.
Also i noticed a problem with the material slots. Wanting to create a dynamic material instance for Slot 5 to change the texture parameter, the actual slot ID could be 34, or 56, because it is assuming the “superficial” material IDs!
Also, the root problem of this thread was never talking about LOD1. There seems to be a confusion here!