Correct me if I am wrong, but as I understand it, it is still legal to tackle a player by grabbing his hair.
If that is true, why would any offensive playmaker who takes the game seriously grow his hair far outside his helmet? It not only gives the defense a 2nd chance way to tackle you, it gives the defense a legitimate way to injure your neck.
If I were the HC, I'd request that hair not be grown outside the helmet except for maybe a couple inches. I'd bet that they're not allowed to force that rule but I'd want my team to have every advantage possible and to not give an opposing team an advantage.
Personally, outside of the game I don't care much about hair length.