Lush cave features sometimes don't generate above chains that support mineshafts

The Bug:

Lush cave features sometimes don't generate above chains that support mineshafts.

Here is an example:

Version: 1.20.1

World Type: Single Biome, Lush Caves
Seed: -5890672563739958369
Coordinates: /execute in minecraft:overworld run tp @s 128.22 -36.00 17.25 296.41 -64.50

Steps to Reproduce:

1. Generate a world with the world type and seed provided above and teleport to the given coordinates.

2. Look closely at the blocks above the chains.

3. Take note as to whether or not lush cave features sometimes don't generate above chains that support mineshafts.

Observed Behavior:

Lush cave features sometimes aren't generated.

Expected Behavior:

Lush cave features would be generated.