I know some of those I really have no idea what they do. Like all the SSAO (Screen space ambient occlusion) stuff.
Here's more info on that... which is apparently something groundbreaking in the 3d world.
The PDF file in that first post, if you scroll down to the SSAO part, it's apparently a control for how the light and shadows are rendered. If this guy's tweak is too dark, perhaps lighting it up a little will work but seeing the pdf's with/without SSAO rendering it's a HUGE graphics difference so I can see where it could make the lighting more dramatic in the game.
So he may be onto something, it just may still need to be tweaked.
I'm wondering if SSAO is responsible for a big peformance hit and that by lowering it and changing the shadow levels he's sort of trying to compensate to get better frame rates and still have good looking shadows.