@harkenn: You misread the post before. It said, "500 rounds since conversion ... to Legend" which is true to all experience the community has. Add a 60.000 average threshold to become a Tour Legend.
It's not official, but some mods have pointed to the public requirement lists as "good guesses". I have yet to experience any proof of the opposite.
Your statement concerning the rise from TM to L is almost correct: It's 50 ranked or tournament rounds (9 or 18 holes) on courses of Par 60 to Par 80, and it's a precise 61.00 average (or lower).