Put the summary of the bug you're having here

What I expected to happen was...:

I wouldn't be able to place the shulker box where an entity was occupying, especially mobs, items can be displaced but vertically in this situation.

What actually happened was...:

It displaced me as well as other entities such as villagers and thus I can stack them under any entity, (so long as I have enough shulker boxes), as an easy way of raising entities.

Steps to Reproduce:

1. Get a shulker box.
2. Make sure an entity is on a block.
3. Place the box where the hitbox of the block underneath the entity is and the entity should be displaced on top of the newly placed block.

Additional Notes:

Maybe this is an intended feature like with the piston displacement bug, which I can see as being true.