I find that school of thought useless, personally. Even if it were true that it was only a belief holding us back (I don't think it is, and there's more science out there supporting that than not), if we can't overcome the belief then what does it matter? We're still stutterers. This is just a good way to trap yourself into a circle of self-imposed failure, because you want to overcome something (a belief) that either isn't the cause or simply isn't overcomeable. I don't find that to be a very healthy outlook to have. As for stutterers who have gained fluency... most of them are still stutterers and continue to see themselves as such. In fact, they've just learned how to stutter better. The most visible and restrictive part of stuttering is the struggle against it. Those people have learned how to work within the bounds of their fluency instead of trying to merely expand them.