The right/left horns and ears of a goat cannot be independently retextured

(Issue first appeared in 21w13a when goats were added)
The right and left horns, and also ears of a goat cannot be independently retextured, resulting in them always looking the same. This is limiting to a player's creativity and ability to modify the entity's texture.

Steps to Reproduce:

1. Download and apply the provided resource pack:
   Goat.zip
2. Spawn a goat

Observed Behavior:

Both the goats horns and ears will look entirely red, despite the player seemingly only modifying one of each in the UV map.

Expected Result:

Only one of the horns and ears would be altered, since that is what the player intended to change. The current behavior is unexpected and not resource pack friendly.

Screenshots/Videos: