Following the logic of the end result of the bug report for MCPE-106013 , then this should also be a bug, but in this case should be fixed (Rather than already being resolved and working as intended)

When wearing a mob head (Save the Ender Dragon Head), if a player is using a Character Creator Character and has a large hat or other large head item, it will also be present with the mob head while wearing the mobhead. Helmets hide these large head Character Creator Marketplace items when worn, and was shown with the Turtle Helmet in the noted report above to be working as intended, so the same logic should apply to mob heads as well.

Steps to Reproduce:

1. Purchase a large hat item (Cowpoke Hat is a good example) from the Minecraft Marketplace for the Character Creator.
2. Apply the large Hat to a Custom Character in the Character Creator and save it to the said Custom Character.
3. Make sure you have the Custom Skin with the large Hat on as your active Character
4. Load up a world in Creative Mode and give yourself each of the mob heads save the Ender Dragon Head; or Load up a Survival Mode world where you have them all save the Steve Mob Head. Then try on each mob head.

Observed Results:

Both the large Hat and the Mob Head appears on the player's head (Save using the Ender Dragon Head this way)

Expected Results:

As with the logic behind the end result of MCPE-106013, only the mob head should appear; the large hat should be hidden.