Neat find! I compared these settings:
A. RGB sliders at 1.00, ISO 1600
B. RGB sliders at 1.99, ISO 800
My initial observation was that B has more noise, and more detail in the highlights. Upon further observation, it appears that B is actually significantly sharper than A, which contributes to the perception of more noise. I do not believe there is any reduction in noise, nor any benefit for low light performance; however overall detail and highlight clipping is improved.
These observations go for both Gamma DR and Normal.
And I confirm that setting the RGB sliders lower than 1.00 simply moves the clipping point and does not grant any advantages.