Everything is related, but in the case, likely very little. Stuttering could contribute to your defense shell you’ve built around you, but so could many other factors. Empathy can be described as a learned trait, not innate for everyone. So it’s possible you haven’t learned it to the extent the therapist is noting. I personally think most people don’t have a lot of empathy, simply for the fact that their own life is difficult and why should they care about yours. It doesn’t make much evolutionary sense to have lots of empathy.