The bug

Bonus chests are intended to contain a sample of every possible Overworld wood type. Despite this, bamboo planks appear to be incapable of spawning inside of bonus chests.

How to reproduce

1. /place feature minecraft:bonus_chest
2. Repeat as many times as is desired
3. Check the contents of each chest

Expected results

Bamboo planks would eventually appear inside of a chest.

Actual results

They do not.