Bamboo can grow to a maximum of 256 blocks tall but not 12-16 tall

it can grow max to 16 block, but when you're placing it you can stack that to the hight limit

This is intentional and the same with cactus and sugar cane, you can still place more on top, it just won't grow higher than 12-16 blocks (3 blocks for cactus/sugar cane).

oh, i'm wrong, thank you

so how to delete this question?

You can't delete reports, a moderator has to come by and resolve it.