Don't think either have anything to do it with it. The Gnat was flying before the report was published. If you go by severity then all Airbus should have been grounded immediately after the Germanwings tragedy but weren't.
At the end of the day if you carry out a risk assessment on a Hunter under new regulation of basic transit flights with no aeros, it would show there is no greater risk than a Boeing 737. After all to establish risk you have to look at the hazard and its severity against the likelihood. In this case yes the hazard could be deemed high (but so could a Boeing 737) but the likelihood provided all the safety measurements are in place such as weather, trained experienced pilot, flight restrictions, good maintenance is low (for both) making this an accepted low risk. After all no flight is ever 100% safe, so if this is the CAA target it will never be achieved.