I noticed in Taiga biomes that when you have the "snow layer" block on top of leaves, it does not decrease the light level. It seems as if the "snow layer" block is completely transparent.

What I expected:
For the light level beneath the leaves with snow layer to decrease.

What happened:
Light level did not change.

Picture 1: Leaves with snow layer, light level is 13 under the center.
Picture 2: Leaves without snow layer, light level is 13 under the center.