Nothing, it's just semantics for people who prefer arguing about "stuttering is incurable" instead of actually doing something more constructive. Personally, if I don't have any unnatural speech-related fears anymore and I can avoid being perceived as a speech-disabled person (without constant struggle, i.e. covert stuttering), then why shouldn't I label myself as being "cured"? Is there anything in my body/brain that's completely different compared to someone who never stuttered?