Lush caves and dripstone caves are naturally-generating overworld biomes, and as such it would be expected that they count towards the Adventuring Time advancement. This, however, does not seem to be the case.
- Lush Caves
- Dripstone Caves
- Kill a monster
- Go to a cave biome listed above, taking care to not go into any other biomes
- Open up your advancements
Notice only one biome has been accounted for (the spawn biome)
Entering one of these biomes would increase the number of biomes shown as being entered, and would be a requirement for the advancement.
The advancement seems to completely ignore these two biomes.
The ability to see in-game what biomes have been entered so far for this advancement would be far more convenient than it is currently, both for those trying to get the advancement and for debugging it like here. This could also apply to other advancements such as A Balanced Diet and Two by Two.