Your understanding is pretty much spot on.
I’ve always assumed the 6 shadow maps in Lighting are reserved for doing a combined lighting / shadow pass, rather than the traditional lighting, then darken area’s that are in shadow. This combined approach has many advantages:
- more accurate spectacular highlights,
- I believe better handling of colored lights and shadows,
- more accurate blacks.
- multiple shadows blend nicely,
- no double darkening of shadowed surfaces
This is because when rendering an area of the material that is not lit, the shader will output mostly no color information, which is more correct than rendering the material as lit, then applying a layer of darkening (the shadow pass) over the top.
… I did some work on this a while ago, my version does what I think Lighting does: Shadows casted on unlit polygons - #9 by thetoucher