I have had similar experiences. I haven't attended a lot of these programs, only one called the Stutter with Confidence program. I'm from Canada but the program was offered to people across different timezones via zoom. The program was created by a severe stutterer and he came up with tools to help overcome blocks and tackle underlying emotional / anxiety part which makes people avoid speaking. From my understanding he took inspiration from other programs and formulated his own. We learned the techniques to overcome blocks then we did cold approaches in the mall for 3 days. Ever since that program, something changed about my stutter. Before the program, my blocks were more persistent and harder to get past. It seemed impossible to say the word and it was even more dreadful if I couldn't replace it. Now I find that blocks are shorter because they're much easier to get over. I did the program Feburary of 2021. The only research backed program is the HCRI program which has been around from the 1900's. And there's s speech program in Toronto Canada run by the Speech Institute and they say they only use research backed methods to treat stuttering.