Quote by Nick Gillard states the tier systems were made by Lucas
"The fighting has evolved in these last three movies considerably," says Gillard. "George Lucas works on a system of levels. So, on The Phantom Menace Obi-Wan would have been like a level six or seven. Now that we're on Episode III he's actually a level eight. When you move up the levels, it affects the style of fighting."
Found this on a 2005 TheForce.net post. Apparently from a homing beacon article.