It isn't uncommon. It's similarly weird for me. I did speech therapy a while, and literally never stuttered in the speech therapy room. I don't stutter if I don't have time to think about it because I'm angry for example. I don't stutter if I act a voice. I replace words I know I will stutter with ... The therapist told me people's stutter just looks differently, and sometimes it looks like mine. Also, btw, speech therapy didn't help. The only thing that really helps me is generally feeling better about myself, and the better I feel the less I worry the less I stutter.