x-ray using tree leaves with graphics on fast

there is a bug that if you use it, you can see all the caves, mines or spawners, like an x-ray. its simple:

1.put the graphics on fast.
2. get a minecart, a rail, and tree leaves.
3. place the leaves in a zone of the mine.
4.put the rail and the minecart below the leaves.
5. sit on the minecart and enjoy the x-ray

i dont know if you already know this bug but i liked to report it and know if you can fix it.