If you suck at singing, you'll wreck your throat and need surgery to fix it. That's a large part of what vocal coaching is for. In that sense, there's definitely a "wrong way" to do it.
Empirically that doesn't seem to be true for many areas of rock--- there are singers singing "wrong" with no surgery for 30+ years. Note that she incorrectly predicted that Ozzy Osbourne would have a short career based on the way he was singing, when in fact he had an exceptionally long and successful one.
From an artistic perspective, in some areas an operatic-style voice is just inappropriate. Operatic vocals on a punk band might be an interesting novelty, for example, but it's not usually what you want; you usually want something more like this: http://www.youtube.com/watch?v=xGjk1Y_j8QE
(From that perspective, metal was a fairly good choice for this interview, because operatic vocals are often appropriate in metal.)
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.
Among singers who have damaged themselves singing incorrectly are Freddie Mercury, one of the best rock singers who ever lived. Over time, he lost his range and stamina, and had to schedule tours in such a way that he had ample time to recover in between performances, otherwise he would lose his voice (this happened once).
I haven't heard him in a recent live performance, but reportedly Robert Plant has also ruined his voice. One person said that he "sounds like Winnie-the-Pooh".
You have to be really careful when extrapolating like that. For example, you could train as hard as Michael Phelps but you'll never swim like him; you weren't born with his flipper-like feet and extraordinarily long arms. What will probably happen is that you'll just burn out.
The people at the top of any field you will find combine hard work with genetic predisposition. They can be an inspiration sure, but imitating them is unlikely to yield the same results.
I think if you look at what she said about Ozzy there is a bit of truth in it. He may not have had a short career but at the end of his career you couldn't understand him at all. Moreover, in that show he did a few years back he is almost completely incomprehensible. Maybe it's from drugs? Maybe alcohol? Maybe he did it on purpose? It always sounded to me like he had a cat in his throat.
From an artistic perspective, in some areas an operatic-style voice is just inappropriate. Operatic vocals on a punk band might be an interesting novelty, for example, but it's not usually what you want; you usually want something more like this: http://www.youtube.com/watch?v=xGjk1Y_j8QE
(From that perspective, metal was a fairly good choice for this interview, because operatic vocals are often appropriate in metal.)