I created a new world and had the seed be "Kesha" because she is my favorite Celebrity. I enabled bonus chest in the options, but when the word generated, there was no bonus chest in the world.
I then created another world with the same seed, and the same issue occurred, despite the fact that bonus chest IS enabled, no bonus chest.
It seems that the bonus chest does not spawn in this seed despite enabling the bonus chest.
The bonus chest does spawn, but it's spawned above the water, see MC-29613.