I rarely use Solid Inspector and don’t even know if such a function is part of it. But yes, that is what I’m asking: correct face orientation. This should be built in, not filtered out by a plugin.
Why?
Well, SketchUp is capable of filtering geometry to see if they are solids, to return (for instance) their volumes. But that can lead to incorrect sums.
If the “correct face orientation” rule is built in, then sums of volumes will be correct.
SketchUp seems to be heading to be a BIM application. Treat Solids correctly and give users the extra option to assign a material (not its texture on the surface!) to it, That would help in developing SketchUp towards using this material for section cut fills. This may look like what Skalp is doing. I don’t use Skalp though. So yes, your second guess may also be right.
True Solids should have material, either applied by the user or default if not (yet) applied.
p.s. In November I had a short conversation with one of the developers of Skalp (at 3D BaseCamp Benelux) and mentioned that I felt SketchUp should only fill loops from section planes with solids. From what I understood, they agreed.