He must have a friend who is a legend that he played match play with. If you play match play with higher ranked players you can lower your score and move up quickly. Sandbagging is more when they are hacks shooting in the 50's and winning a tonne of credits in the process.
As far as I know it's completely acceptable to play match play with friends and have them throw games in order to move you up through the tiers. I don't think it's right. If your going to move up it should only be done through stroke play and tournament stroke play games. I don't play match play to move up. I like to earn it .
It really does not benefit this player you speak of to move up quickly and play like a hack though he is a legend. Also sounds like he isn't going to be making any credits in this game by winning them. Just making the game harder for himself I suppose! :)
Mandy