I can see how some people could feel that way. It's pretty impressive for anyone to achieve high levels of fame despite the fact that they stutter imo. Stuttering makes just about everything harder, so it's probably safe to assume they've achieved some level of fluency along the way. Success usually breeds more success & confidence, so talking to the media may not trigger nearly as much stress as it may have in the past, making it easier for them to remain fluent in those situations.