The sky darkens when I stand in shadows.

While installing 13w39b today I noticed a change in the lighting engine. When I stand in a dark place, the scene darkens. I do not think it makes sense: the sky should not dim because I walk under a tree or because I am inside my house. The blocks already have a light level, I do not understand why it should affect ambient and directional lighting.

If anything, I would expect the exact opposite to happen. When I stand in the shade, my eyes get used to the darkness around me, which means that the whole scene should bright up, the sky could even blind me. And when I am in broad daylight, I should not be able to see anything inside the cave in front of me.

Is it an attempt at deciding the color of the fog independently from one's altitude?