Llamas suffocating/drowning when bobbing in water with block above

When a Llama (baby or not) is bobbing in the water, it is suffucation or drowning with a block above its head (pic. 1).

Just a block above it's head does noting (pic. 2).

A cow bobbing in the water won't suffocate/drown (pic. 3).

This is quite strange because the baby llama has a smaller hitbox than the cow..