Not sure if this is true but it makes enough sense to me: If you can speak fluently by yourself or to pets or something then the problem is entirely psychological. If it’s entirely psychological then things that have no purpose other than making you feel better will put you in a better headspace/mental health which will improve your speech. If you think about it speaking is like dnd combat. Every word you speak has a roll associated with it. The chance you stutter on a word depends on stuff like 1) how hard the sound is to make naturally for you (this can be thought of as damage) and 2) some complicated underlying psychological equation that goes against your natural stuttering (this depends on how you’re feeling and a bunch of other shit we can never know about) (this can be thought of as armor). Increasing passive armor buffs by taking care of your mental health (by working out, meditating, etc) increases the chance you’ll overcome the natural stutter for each word.