What is Pivot in Color Grading?
As you know, the contrast function darkens dark colors further and lightens light colors further. Software without a pivot parameter assume that the point where darkening becomes lightening is exactly in the middle, at 0.5 (for a color range of 0 to 1). Those with a pivot parameter allow to move the pivot point up or down. Shifting the pivot slightly down (e.g. from 0.5 to 0.4) results in dark-medium colors (let's say 0.45) not anymore being darkened, but lightened. 

In your image, the effect is not that visible because most of the colors are already very bright, very dark, or just in the middle.

If you want to lift or lower your midtone details, I would suggest that you use a gamma or midtone control instead.