In my experience at least, I've never met a stutterer that didn't have ANY degree of control over it. The common notion is that we all have our bad days & our good days. Almost everyone I've encountered (myself included) has their own little personal tricks that help them to achieve better fluency, even if it's just temporary. The point I'm trying to make is that most of us are capable of being fluent (to varying degrees) at times. I personally believe that most stutterers aren't severe enough for it to be considered a disability. I believe in most cases there's a high likelihood that there are steps stutterers can take to lessen its' effect on their life, a luxury that people with disabilities don't often have. For those that stutter so severely & honestly have no control over it, I wouldn't be surprised if stuttering to that degree of severity is found to be a symptom of a much deeper root cause. Once we have a better understanding through medical research of course (if we ever get to that point).