Mules or baby horses suffocate when push into a wall

What I expected to happen was the mule or baby horse to live when they were pushed into a wall

What actually happened was the mule or baby horse suffocated when they were pushed into a wall

Steps to Reproduce
1. Spawn in horses
2. Breed them to get a baby horse or mule
3. Push the mule or baby horse into a 2 block high wall
4. They will suffocate