Squawk7777, indeed, some (more) red tape to navigate around. It had to do with the system we use to test the people's skills. Apparently it was cheaper to use this one we use now (which can only "prove" up to level 5) and keep testing people every so many years, than paying royalties/developing another more robust system (which could ascertain up to level 6).
A beancounters approach. But a working approach, nonetheless.