The bug

Mobs in lazy chunks can be killed using /kill, but their death animation doesn't play until the chunk is loaded

To reproduce

1. Set render distance to 2
2. Move away from the spawn chunks
3. Summon ac ow with NoAI

   /summon cow ~ ~ ~ {NoAI:1b}

4. Move 3 chunks away
5. Run /kill
6. Wait for a bit (long enough for the death animation to play)
7. Go back to the cow
   → The death animation is played as soon as you are near the cow