Whatever the words he chooses, I think Zlin has got it right. Leaving aside for a moment, the question of whether or not JAR is a good thing (most people know the answer to that), we have two real factors under debate. The single vs. multi crew aspect, and the piston-twin vs transport jet bit.
Even prior to JAR, the CAA would not allow a pilot that had obtained their IR in a multi-crew environment to fly single-pilot IFR in IMC. So, no change there. Clearly it is tougher to fly an approach to minima, single crew.
Now then, passenger jet, versus piston twin... Start thinking about factors like power-plant reliability, complexity of operation, behaviour in response to failure, performance available, instrumentation quality and reliability, autopilot capabilities... Well, I know what conclusions I draw