Invulnerable boats gets destroyed the same way as a default boat

I summoned invulnerable boats for a custom map.

What I expected to happen was...:
The boat gets destroyed like a normal boat.

What actually happened was...:
I summoned a invulnerable boat and I have drive it to a wall and it gets destroyed. I summoned a invulnerable boat above me and it gets destroyed.

Steps to Reproduce:
1. Summon a normal boat 10 blocks above you: /summon Boat ~ ~11 ~
2. Summon a invulnerable boat 10 blocks above you: /summon Boat ~ ~11 ~

{Invulnerable:1}

3. When it falls in the ground it gets destroyed.
4. Summon a invulnerable boat: /summon Boat ~ ~1 ~

{Invulnerable:1}

5. Try to destroy that boat (in survival of course).

You will expect that it isn't normal because a invulnerable entity have to be invulnerable and you have to be creative.