When you place bamboo on top of a bamboo sapling, it doesn't turn into a small bamboo tree.

To reproduce

1. Don't enable Experimental Gameplay 
2. Place bamboo (for the sapling)
3. Place another bamboo on top of the bamboo sapling.

Workaround

Enable Experimental Gameplay.

Observed
Bamboo doesn't turn into a bamboo tree when placing more bamboo on top of the sapling.

Expected
Bamboo should turn into a bamboo tree when placing more bamboo on top of the sapling.

Note: If you bone meal the bamboo sapling and place bamboo on the bamboo tree (grown by bone meal), you can place bamboo on top of the bamboo shoot but not the sapling. Also the bug might be only be affecting new generated worlds. Issue occurs when Experimental Gameplay is not enabled, the only workaround is to turn Experimental Gameplay on.