Ender Dragon can be attacked by its rider

I can perform melee attacks on the Ender Dragon while riding it, unlike with other mobs.

How to reproduce:

1. Head to the End dimension
2. Execute

   /ride @s mount @n[type=minecraft:ender_dragon]

3. Attempt to hit it

Expected result:

You would be unable to attack the dragon while riding it, because it is your mount.

Observed result:

You can attack the ender dragon