Baby horses, donkeys, mules, llamas and trader llamas no longer spawn occasionally when using a spawn egg on a block

The bug

Prior to 19w37a, when using a horse, donkey, mule, llama or trader llama spawn egg on a block (while not looking at an adult animal), occasionally a baby horse, donkey, mule, llama or trader llama would be spawned instead of an adult animal (see MC-135098). That does no longer happen.