When bonemealing a bamboo on the top of the shoot, player is put inside of bamboo shoot when the shoot rises.

I wouldn't consider it as a bug. Its the same reason why you sufficated in trees a few years ago. In response Mojang addet a "feature" which tries to push you out of solid blocks if there is free space next to that block you sufficate in. But as mantioned earlier in my comment it works with solid blocks. the bamboo is no solid block so it won't push you out of it. 

Invalid for the same reason as MC-88639.