If a chicken jumps up to a 1-block tall opening, they take suffocation damage, even though they are small enough to go through.

What I expected to happen was:
when a chicken jumps up to a 1-block tall opening, they shouldn't take damage.

What actually happened was:
the chicken, when jumping up to it, takes suffocation damage. If done over and over, they will die.

Steps to reproduce:
1. Create a 4 x 3 pad one block above the ground.
2. Make a roof about the same size above, allowing for a 1-block opening. See attchment
3. Spawn chickens and lore them to the other side. When done, the chickens will go through the opening. Upon jumping to go through, they take damage.