(solved) Can someone explain this- (UV Local View)

I’ve got a few cupboard doors that I’ve assigned a single material to, called: Unit2CupboardDoors.
(Image 4 confirms there is only one material assigned)
But when I export it to Substance Painter as an obj, there are suddenly 2 materials and the one has _NONE affixed to the end of it. ie. Unit2CupboardDoors, and Unit2CupboardDoors_NONE. (Image3)

After doing a bit of digging, this is what someone said:

Sometimes (always) this happens in blender if you have images already assigned to certain uvs. If you go to uv view, are there any images assigned to any of the material groups? If so, you need to x them before you export. Don’t know why it happens, but it does.

I can click on any face, and it doesn’t seem that any images are assigned.
But, when playing around, I went into the UV view, and clicked on View > UV local view, and, true enough, the faces that show up as “Unit2CupboardDoors” in Substance painter disappear from view, and only the “Unit2CupboardDoors_NONE” remain. (Image 1 and 2)

I can assign an image to it, unassign it by clicking X, and nothing changes.

Can someone explain what is happening here, and how to get rid of it / fix it?

Edit It looks like it only works if you go back to Blender internal render, and assign an image texture to all the faces (in UV view) and then delete it by pressing X. If you do it while in cycles view, it doesn’t assign / unassign it.

You could write an answer instead of editing the question to actually mark the question as solved…
That said I doubt I get what happens with that cupboard there. Cycles doesn’t assign face textures like Blender render does, hence there’s no reason to open / remove image with UVs selected in UV editor in Cycles, it doesn’t change anything for it. It does for Blender render but I don’t see why and how it changes things for Substance. I would exit UV local view and once again assign all faces to mentioned material.