Attachables & Entities sharing Namespace

Remake of MCPE-138832
Issue still exists in latest minecraft version being 1.21.1 at time of writting, as per previous issue, this bug has existed as early as 1.17.x

Steps to Reproduce:
1. Create an resource pack with an attachment file for any of the following items: Chicken, Rabbit, Cod, Salmon, Pufferfish, Arrow, Egg, Ender Pearl, Lingering Potions, Snowball, Splash Potions. 
2. Change the "textures": {"default": "textures/entity/..."} to anything
3. Load into a world.
4. Find or Spawn the entity you modified

Observed Behaviour:
The game will now somehow use the item texture as the entity texture and also has no animations.

Expected Behaviour:
with the supplied file (found below), nothing bar the item texture in the players hand should change.

 

Notes: 

I will also attach a copy of the attachment file used for debugging. (excuse the geometry file, I cannot find a good refernce to say what the vanilla file would be, for this type of item.)