I don't think that matters as long as probation services and the police are also involved who will have more professional experience of offending behaviour and set guidelines.
The Circles just seem to be a community organisation to stop people getting isolated and offer support. I think people often slip into old habits (of any kind) when they are depressed or bored or lonely (smoking, substance abuse, overeating, relationship patterns ) so trying to support sex offenders through those periods makes sense. Who better to do that than do-gooders no matter how naive.
Yes, it is the support which is beneficial and liaising with police and probation officers keeps the whole on a professional level.