Summary
When Experimental Gameplay is disabled, it is not possible to place bamboo on top of bamboo saplings. Since all of the other 1.8.0 features are out of Experimental Gameplay, I assume this is not intended.
Steps to Reproduce
Create a world with Experimental Gameplay disabled.
Give yourself bamboo.
Plant the bamboo.
Try to place bamboo on top of the bamboo sapling.
Observed Results
Bamboo cannot be placed on top of the sapling.
Expected Results
Bamboo can be placed on top of the sapling.
Wait is this still possible as of 1.16.x betas?