When I double tap A on my controller to fly there is a lighting bug

When I double tap A on my controller to fly, the light gets a tiny bit darker or brighter on the tops of the trees.

Steps to reproduce

1. Go into a swamp biome (the biome I tested this in)
2. Go to y=100
3. Continuously press A on the controller
4. Observe the tops of the trees

What I observed

When pressing A many times, the trees' leaves got brighter and darker just a little bit.

What I expected

When pressing A many times, the lighting on the tops of the trees will at the same light level, not get brighter and darker just a little bit.