Mobs holding the mace will not deal extra damage when falling down on their target, even though you can see and hear the smash attack happen.

Steps to reproduce:

1. Build a 5 block tall pillar
2. Summon a husk on top of it:

   /summon husk ~ ~ ~ {CanPickUpLoot:true}

3. Give the husk a mace
4. Stand at the base of the pillar in Survival mode and allow the husk to fall on you

Observed result:
The husk falls on you, performing a smash attack with particles and a sound effect, however you take normal damage from the attack.

Expected result:
You would take extra damage from the attack (enough to one-shot an unarmored player).