When I was on methadone, and a low dose at that, I was high. High enough to almost nod out at times. Also, a friend of mine got in accident after leaving the methadone clinic, she had just dosed and nodded off in traffic.
IMO, he JUST started MMT, he has along way to go to get his life and thinking back on track. MMT, as well as subs and other treatment, isn't a magical cure. he still has work to do, alot. He is newly off the opiates. If it was me, I would keep the supervised for a bit longer. He needs time to get his brain back on track. And personally, I love the methadone. It got me higher for longer than the oxy. That is one big reason I can't use it for recovery. So yeah, IMO, keep those visits supervised until he has had more time to prove himself.