I was in speech therapy for years and have a similar thing that my therapists never really understood. Normally, according to speech therapists of the 1990s at least, most stutterers will stutter MORE when nervous or unsure of a scenario like with a stranger or doing a presentation. I always had to explain to my therapists that for me it was the full opposite: perfectly fluent doing a graded presentation in front of a whole class/professor or in a job interview, while I’d be stuttering all over the place with my family, friends, or significant others. My theory as a kid was that with strangers, I subconsciously wanted them to see me as an equal with no “disabilities” and make a good first impression, so under the hood I seemed to be handling my fluency better in these scenarios. When with people I was comfortable with, I could “let my hair down” and not worry about making a first impression with them, they love me regardless, hence my fluency suffered with them. Haven’t been to speech therapy in probably 15 years so I’m sure some ideas and techniques have changed but that was my personal situational experience with regard to my stutter.