/fill ... skull | Hitbox Bug

I tried some of the new commands using /fill ~ ~ ~ ~ ~ ~20 skull , it was suppposed to fill the next 20 blocks with skulls as you can see in the command in the chat.

It filled the blocks with skulls but if they were attached to a block in the side, and the hitbox is like above a block

Steps:

/fill ~ ~ ~ ~ ~ ~20 skull