Vanilla bug https://bugs.mojang.com/browse/MC-179383. A close relative of #858 and #859.

For whatever reason, leaves in the Fast graphics mode do not cull the faces of adjacent leaves blocks, completely defeating the purpose of fast graphics altogether to my knowledge. These faces are meant to never be seen in this specific graphics mode, so having them all render anyway makes no sense.

Duplicate of #280.

Evidently I didn't see that one, my mistake