The resource pack attached to MC-236458 offers a complete fix for this issue. Mojang have my full permission to (and are encouraged to) replace the affected vanilla model files with the contents of the resource pack.

The bug

The bamboo shot model references the "tinted cross" template. However, bamboo shoots are not tinted at all.

How to reproduce

1. Extract the minecraft jar file bu your preferred means
2. Navigate to assets/minecraft/models/block
3. Open bamboo_sapling.json
4. Note that it references "block/tinted_cross", like other models such as ferns
5. Now enter the game and place bamboo shoots in multiple different biomes
6. Note that the bamboo shoot looks the exact same in each biome, disproving any actual use of tints

Expected behaviour

Either the bamboo shoot would look different depending on the biome it exists in, or the bamboo shoot model would just reference the normal cross model due to not being tinted.

Actual behaviour

Despite referencing the tinted cross model, the bamboo shoot does not appear tinted.

How to fix

MC-236458 fixes this by making the bamboo shoot reference the normal cross model instead of the tinted cross model.