That's just confirmation bias. I've been to programs where I was perfect in the program, they told me to keep up the practice when I came home and it'll stick. Well for a lot of people it doesn't stick and they're told it's because they didnt work hard enough. This is flawed because it assumes the technique infallable and therefore if you start slipping, it's you're fault. Proof should be affirmative when making a claim, not counter negative. I wish you luck and i've known several people who have had good success with McGuire, but dont hammer yourself if you find yourself trying and it's just not happening. Techniques aren't some inerrable answer for stuttering. In my opinion, they often counterproductive.