I watched the old post https://bugs.mojang.com/browse/MC-1769 ，I see standing inside TNT/Glowstone/Block of Redstone was fixed now, but standing inside tree leaves still can let people see through blocks, if you turn your render quality to fast mode.

To reproduce:
1, change render quality to fast.
2, place some tree leaves, at least 3x2x3, and teleport you inside it.