The bug
When you hold down right click to feed and animal with an item that you can eat, you will only feed the mob once and then you will eat that item. This behavior is simelar to MCPE-56968. For example when you feed an untamed horse with an enchanted golden apple, you will only feed the horse once and then you will eat the enchanted golden apple. This also happens when feeding a baby animal to speed up growing.
How to reproduce:
Be in creative mode
Spawn a horse
Hold an enchanted golden apple in your hand
Look at the horse
Hold down right click
❌ You will only feed the horse once and then you will start eating the enchanted golden apple.
Expected result: You will feed the horse over and over again.
Affects version 1.16.210.59 in Windows 10