Woooww that's really crazy, I went to speech therapy for a few weeks but I can't say it was very helpful, she definitely didn't recommend the BPM thing, but I still appreciate their effort. The BPM thing has a high likelihood in working because I noticed stuttering is connected to a person's rhythm, a lot of times I notice that there isn't really a rhythm in my speech, somehow it doesn't come to me naturally to pause, breathe, say something at the correct timing, and I noticed BPM helps me find some sort of rhythm, I started at 90 BPM and I moved to 100 BPM, I'm pretty comfortable at 100 rn - The whole point I noticed of a metronome is it gives you the ability to remember to give every word its own time and thus giving you a smooth rhythm, also helps with speaking clearly. Good luck!