I think speech therapy might be more effective combined with normal therapy as well. Having a stutter gives me extreme anxiety sometimes and I've heard from others that it can be really exhausting mentally too. It's a good idea to try it and even if it doesn't solve everything I think it'll help a little bit. Also, with covid I'm assuming he doesn't get to go out and talk to a lot of people either. Sometimes when I don't talk a lot for extended periods of time the stutter does get worse. It gets better as I just talk more. Thank you for asking :)