I think it’s a mix of calm emotion and the brain knowing it’s not being judged by someone else so that fear that’s triggered by another persons presents isn’t activated which enhances the stutter. I have the same problem and it’s the hardest part to change about yourself bc it’s emotion/body/mentally tied all in one. It’s tricky cuz if you take eliminate the mental part the body would still go into a state of shock/fear within the moment just cuz it was trained that way for such a long , which can throw off all your hard work to stay calm n not stutter. I swear we’re always at war with our own body, n will be probably till we die. My heart goes out to anyone who has this or worst