I agree with your findings. As many people already said, when you are free from anxiety in situations, stuttering would be considerably less. I think same is the case with your experiment with the bot. I feel that fear of being judged, that you are a stutterer, plays a major role in our stuttering in social conversations. I sometimes feel it's way too complex to explain why I sometimes stutter too much with the same people, with whom I normality stutter less. I think this has got to do with the content of information you are trying to express, which is associated with its own value of anxiety in you. I find it funny and amusing that I never stutter while singing a song.