You're right in that there are clearly people who have been successful this way, but it's a self-selecting group. We don't hear about the ones who are too hard

You're right in that there are clearly people who have been successful this way, but it's a self-selecting group. We don't hear about the ones who are too hard on their larynxes and have to give up early. There's clearly a safety margin in what vocal coaches teach, and I think it's safe to say that Ozzy must be over the margin, but the right side of critical.