In terms of a legend sandbagging as NOT had mentioned, I don't know if I would really call it sandbagging when a guy is labeled as a Legend or Tour Legend no matter what their average. They achieved the level by being a good player, they may not play enough to move the average down much but they did hit the requirement at one point and time.
In my case I play a lot of alt shot and a good bit of blitz. My weakest area in putting so I can hold my own in a blitz game with pretty much anyone, even though my average is north of 60. I could grind away at stroke play games and get my average down under 60 since I have enough ranked rounds to be saturated but I have no desire to do that only for the sake of becoming a sub 60 player or even a tour legend. The slow march to a lower average will happen, I play enough stroke play so that I can see my average slowly move but I still won't never consider myself a sandbagger.
My view is that is a person who keeps his tier well below where it should be, either by artificially inflating his average or not playing ranked rounds so that they will keep the advantage of their tier. Not much tier advantage to a legend.