Withers can't kill armour stands from above

Steps to Reproduce:

1) Place 4 blocks down forming a 2x2 square on the floor

2) Place an armour stand on each of the 4 blocks

3) Stand in the middle of the 4 armour stands

4) Run "/summon wither ~ ~5 ~"

5) The Wither is unable to kill you as its skulls collide with the armour stands (the armour stand hitbox is taller than the player's) and the armour stands don't break