Double sea grass on amethyst geode and on coral blocks can be generated in 1 block (top only)

Summary:
Double sea grass on amethyst geode and on coral blocks can be generated in 1 block (top only).
1.19:

(coral blocks)
Seed: -732078047
Coords: 12 48 -410

(amethyst geode)
Seed: -732078047
Coords: -1832 38 -1833

Steps to reproduce:

1. Create a world with the specified seed.
2. Teleport to the specified coordinates.
3. Consider how the double sea grass was generated.

Observed results:
Double sea grass generated in 1 block (top block only).

Expected results:
Double sea grass will not generate 1 block, half.

Image: