I cannot understand how this occurred; I've never heard of something like this in over thirty years of aviation. A SVFR clearance is issued so that a pilot can depart visually in circumstances where IFR would otherwise apply.
If the weather at the field seriously deteriorates after the aircraft departs, I would say that it's irrelevant to ATC unless the pilot himself requests assistance. An ATCO should only ask the pilot if he is still able to continue under SVFR or continue under IFR. Effectively this unrated PPL was ordered to return (from acceptable VMC) to attempt VFR flight in IMC.
I hope this was a one-off incident, never to be repeated and that it has been fully publicised around all ATC units. Obviously, it could have resulted in an aircraft accident and the pilot has obviously learned his personal lesson from the incident.
One thing that could have helped ATC here. Do all ATC units determine if all pilots are IMC rated at time of booking out if a SVFR clearance is requested or deemed necessary by ATC? I don't think they do; I think they should do so.