The ender dragon can take damage from firework rockets shot from a crossbow while perched

While the ender dragon is perched, it can take damage from firework rockets shot from a crossbow, although depending on the angle it may not (see MC-313168).

To reproduce

1. Create a new world

2. /execute in minecraft:the_end run teleport @s 0 72 0

3. /kill @e[type=end_crystal]

4. /item replace entity @s weapon.offhand with firework_rocket[minecraft:fireworks={explosions:[{has_trail:1b,shape:"small_ball",colors: [4312372]}],flight_duration:1b}] 64

5. /item replace entity @s weapon.mainhand with minecraft:crossbow[minecraft:enchantments={quick_charge:3}]

6. /data modify entity @n[type=minecraft:ender_dragon] DragonPhase set value 3

7. Shoot the ender dragon from the side or behind while it is perched, and observe that it takes damage

This may be intended for the same reason as MC-311111 (whatever that reason is).