I use it to enhance the contrast of textures (eg to pop out the veins of woods or cracks in the concrete). In Photoshop, first by desaturate it, then increasing the contrast of the pass and changing the blending mode to softlight or overlay.
But because there's some shading in the pass by doing so I also introduce the shades.
I guess you will be tired of hearing comparisons, sorry, but just to understand what I would need, back in the days I used to use this technique with the VRayDiffuseFilter without problems.
I've attached an image of my CShading_SourceColor (diffuse). The shading is more visible in the round geometrys with no textures where I wound suppose to see full color without shades.