Baby Mobs -Graphic Hitbox Issue

When I summoned a baby zombie villager and used "/execute @e ~ ~ ~ replaceitem @e[r=2] slot.armor.head minecraft:pumpkin"

What I Expected was That:
The baby zombie villager would have a pumpkin head

What Happened Was:
The baby zombie villager had a pumpkin head, but it was 2 blocks higher than the baby zombie villager.

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Note:
This didn't happen with a normal baby zombie, only with a baby zombie villager