The mushrooms on the red and brown mooshroom cows cannot be independently retextured from their block textures

The mushrooms on top of the red and brown mooshroom cows cannot be independently retextured from their respective block textures.

Steps to Reproduce:

1. Download and apply the following resource pack:
   Mooshroom.zip
2. Spawn a red or brown mooshroom cow

Observed Behavior:

Despite the player only choosing to modify the red and brown mushroom block textures, the mooshroom entity will have changes made to it's texture.

Expected Result:

Only the block textures would be changed, as that is all the player intended to alter. Having the entity's texture be modified due to a change made to a block's texture could be unexpected to some players, and not resource pack friendly.

Screenshots/Videos: