Decorations and terrain can generate inside of structures

The Bug:

Decorations and terrain can generate inside of structures.

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

Here are some examples:

Seed: -6533926018995126751
Coordinates: /execute in minecraft:overworld run tp @s 171 68 869

Steps to Reproduce:

1. Generate a world with any of the seeds provided above and teleport to the given coordinates.
2. Look closely at the terrain/decorations inside the said structure.
3. Take note as to whether or not decorations and terrain can generate inside of structures.

Observed Behavior:

Decorations and terrain can generate inside of structures.

Expected Behavior:

Decorations and terrain would not be able to generate inside of structures.