This only affects versions below 1.21.5
After the fire nation attacked- i mean cold and warm mobs were added the files were put in Stellar Tweaks/1.21.5_up/assets/minecraft/textures/entity/chicken
Yes this means the assets were duplicated for backwards compatability
Yes we hate it too.
Also, for some godforsaken reason the chickens only work when they're not in an entity/chicken folder (pre 1.21.5)
We are just as confused as you.
The Optifine format is a mess.