Mansion cobblestone foundation does not replace decorations

The Bug:

Decorations can replace parts of mansions when generating.

Just for clarification reasons, decoration blocks are blocks such as grass, ferns, seagrass, etc...

Here is an example:

Version: 1.21.4

Seed: -7979010454089259359
Coordinates: /execute in minecraft:overworld run tp @s -782.93 70.00 -515.35 148.44 18.20

Steps to Reproduce:

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

2. Look closely at the generation of the mansion and how nearby decorations intersect it.

3. Take note as to whether or not decorations can replace parts of mansions when generating.

Observed Behavior:

Decorations can replace parts of mansions.

Expected Behavior:

Decorations would not be able to replace parts of mansions.