When a resource pack add-on provides textures for blocks that don't exist, the game seems to partially apply these textures to blocks that do exist, in certain situations.

In the screenshots, you can see a texture intended for the "Mud" block (which only exists in 1.19.0+) is affecting the textures of other blocks, as well as their wall and stair variants.

1.19 UPDATE: Loading the pack (unedited) into 1.19 provided the expected results. This means that the issue was indeed with the game and not with the pack. 1.19 may need to be tested with nonexistent block IDs to see if they cause problems like they did in 1.18.

Steps to Reproduce:

1. Install the attached resource pack add-on (which only contains textures for mud and muddy mangrove roots).
2. Create a new world .
3. Activate the resource pack for the world.
4. Open your inventory and search for affected blocks (it varies).
5. Observe.

Observed Results:
The textures of some blocks, and their wall or stair variants were affected by the resource pack add-on,

Expected Results:
No textures were affected because Mud and Muddy Mangrove Roots aren't available in the current version.

Screenshot(s):