When you get a Wither with the NoAI NBT set to 1 and get it under half health, the Wither will get armor on it.

What I expected to happen was...:
The AI-less Wither should not have armor when it's under half health.

What actually happened was...:
Instead, the AI-less Wither actually will get armor when it's under half health.

Steps to Reproduce:
1. Summon a Wither using /summon WitherBoss ~ ~ ~

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2. Get it under half health to see its armor appear.