When breeding horses, the baby appears fully grown but still acts like a foal

What I expected to happen was when breeding 2 horses with golden carrots, a foal was produced (that is visibly smaller that adult horses)

What actually happened was when I bred 2 horses, the foal was not smaller than the adults, it was visibly full grown but still had foal characteristics (e.g. nothing happens when right clicking to get on the horse, legs move quickly and they move a far distance when pushed, still have foal noises when hit/killed etc). The 'foal' can still be fed to be grown into an adult horse, but there is no visual of the foal growing or getting bigger, the foal just rears when full and has turned into an adult horse. (The attachment shows a baby horse just bred, the black one with no saddle)

Steps to Reproduce
1. Give a golden carrot to each horse to breed them
2. The foal is produced but it is visibly the size of an adult horse