I don't know how there can be a formal definition of "bagging" period. Unless you see a guy throwing off on purpsose (shoots a the 7 when he leaves a 10), we all shoot a different score from game to game. That's why they call it an average. Lane conditions, approaches, balls, houses, pins, all vary from night to night. I can throw the ball horrible one night and shoot 700+ and then turn around the following week and have a great feel and shoot only 600.
I feel that there's not much difference between someone who averages 190+ up to 210+. That person still has the ability to shoot good scores, just unable to make a quick adjustment or make their spares consistently. The way that equipment is these days, anyone can shoot a good set on any given night. It's called a "buzzsaw" and I'm sure that we've all run into a few of those.