As kids, we used to underinflate the old pig skins as it made them easier to grip and throw. Not only that but it made them easier to grasp once they got to you (if they ever did). I could throw a ball much farther if it were a bit underinflated because I could grip and rip it rather than having to rely on the threads. Now I wouldn't doubt that a ball thrown by an NFL QB would travel better (minutely) if more inflated but it would still be easier to catch and hold onto if underinflated. And it would still be easier to fling it all over the field. You might even be able to put more force on the ball with the confidence of grip.