Hal never said he learned to aim from Ralph Greenleaf. In fact, he stated that Ralph was an "idiot savant" when it came to aiming and ball pocketing. Hal claims CTE was invented by no other than himself.
However, there are two sides to every story. Check out Jimmy Moore:
http://www.youtube.com/watch?v=Bc2Q5lh_VRk
http://www.youtube.com/watch?v=QHtRjbHZU2g
From what I've gathered (from Blackjack and others), Jimmy was friends with a guy named Fez Kasson (RIP) who, like Hal, was also a road-partner of Greenleaf. According to Fez, Ralph "discovered the system for everything" and passed it to him (who later showed Jimmy). Now, whether Ralph figured it out or learned it from Hal-- we'll never know beyond Hal's word it's his.
Either way, CTE is a super-old system. It's been a hot topic on azb over the last few years. However, the system is older than many of us have been alive and that's a fact.
So, you have two legs from Greenleaf: Fez and Hal. People surrounding both learned how to pivot. Who TRULY knows which of the three invented it (or if they got it from someone before them). That's the earliest it can be tracked (in its current form).