Warden's Sonic Boom cannot kill witches

The warden's sonic boom deals reduced damage to witches, and since witches can heal themselves faster than the warden can attack them, a warden cannot kill a witch.

How to reproduce:

1. Build a pillar that is 3 blocks high.
2. Spawn a witch on top of it.
3. Two blocks above the highest block of the pillar, place a solid block one block away on each side so the witch can't escape.
4. Place a block above the witch.
5. Spawn a warden on the ground and watch it attempt to kill the witch.

Expected result:

The warden would be able to kill the witch with its sonic boom attacks.

Observed result:

The warden keeps attacking the witch with its sonic boom to no avail, as the witch heals itself after every attack.

Video demonstrating the issue: https://www.bilibili.com/video/BV16U4y1m74v