This is the image with no indirect lighting.
http://s29.postimg.org/6e936dqkl/image.png
This is the image with indirect lighting. (Please notice saturation went just sh*tty)
http://s29.postimg.org/hy4q6xkud/image.png
And this is the image with indirect lighting saturation zero (Please notice it is just same)
http://s29.postimg.org/i5wyh6l6t/image.png
So indirect saturation is not working.
And please do not ask if I built my light or something.
It was also not working UDK which I reported it 7 months ago.
https://forums.epicgames.com/threads/984965-Indirect-Lighting-Saturation-Does-Not-Work-At-All
I have a suspicision UDK and Unreal 4 has same code with indirect lighting saturation part.