Stuttering is not only 'improved' when you are really working on something. Sometimes it can just improve simultaneously or even totally disappear without any other helps, sometimes it can also deteriorate out of blue. It's also implicating your lucks. But still I don't recommend you to give credits to any 'dr' who is flaunting he/she can cure your stuttering, like I said if he/she was really onto something this sub and other stuttering communties were rn celebrating.