When shearing a mooshroom or sheep, the mushrooms or wool will fly out in all directions from the top of the relevant entity. However, when shearing a bogged, the mushrooms will barely fly out from the bogged's feet. I believe this to be an inconsistency in gameplay as players will expect the items to come from the relevant position on the entity (the bogged's head in this case) on all entities.

Note that Bedrock Edition spawns the mushrooms in the vertical center of the bogged.