Armadillo roll stays longer and can't be hit

Why does the armadillo take a few seconds to unroll? Why can't you make take like a minute to unroll. So the player must be more careful around the armadillo. And aren't they armored? Why can the player hit the armadillo when it rolled? Isn't the rolling thing supposed to protect itself? Make the armadillo invincible (at least the player can't hit it) to be more accurate. Thanks for reading my idea.