The Bug:

Big dripleaves within lush cave biomes can generate on top of invalid blocks.

Here is an example:

Seed: 4373241205666815302
Coordinates: /execute in minecraft:overworld run tp @s -11750.00 0.00 -23450.33 -171.05 33.94

Please note that you may need to fly to the given coordinates in order to reproduce this behavior.

Steps to Reproduce:

1. Generate a world with the seed provided above and teleport to the given coordinates.
2. Look closely at the block that the big dripleaf is supported by.
3. Take note as to whether or not big dripleaves within lush cave biomes can generate on top of invalid blocks.

Observed Behavior:

Big dripleaves can generate on top of invalid blocks.

Expected Behavior:

Big dripleaves would not be able to generate on top of invalid blocks.