Entities clip through blocks in superflat worlds

The bug

Entities can clip through blocks in superflat worlds. The height were they can clip through blocks, depends. Sometimes they can clip through blocks at y=5, sometimes y=15, etc.

How to reproduce

1. Create a new superflat world

   Seed: -6264591895041810113
   

2. Run

   /fill ~-20 15 ~20 ~20 4 ~-20 stone
   /fill ~-20 18 ~ ~20 15 ~ stone
   

3. Spawn or summon few wolfs on the other side
4. Switch to survival mode, and hit them so they get mad
   → The wolves clip through the blocks