The requirement for CPL level knowledge for a FI has been an ICAO requirement, probably dating back to the 1940s. The UK chose to ignore it, probably because we ran a Flying Instructor Course based upon the RAF training system, thanks to Ron Campbell. This was accepted at the time as meeting the CPL theory requirement.
Europe has followed the ICAO line so we now have CPL level theory and a beefed up FI course . In the USA the FI course doesn't exist and never has. Now that the JAA has dissolved and EASA governs in Europe, the CAA has no remit to change anything:
Nice to hear that the CAA has finally recognised the shortage of instructors in the UK and is proposing to do something about it.
unfortunately, there is no foundation for this statement, as they are no longer in charge!