It looks legit to me. His stats
show that he's pretty good with approaches, sand saves, and scrambling, and that he plays a lot of coin games. Maybe he got favorable green speeds and wind directions during his Showdown rounds.
Doesn't everyone, in the same league, get the same green speeds. I don't really see his stat's as that good, and some are wgt nonsense, but I also don't see that they need to be.
Yiannis, yes there are cheats in the showdown but that's mainly multi's and perhaps, depends how you view them, restarts. They only benefit at rookie.
Lets say he usually shoots -10 in tournaments, and ignore the fact that those of us below top level are inconsistent. In the Veteran Showdown he's wearing apparel and is off shorter tees, add to that a plethora of par 5's (5or 6?) from these short tees with his boosted driver etc. The slower greens on many holes also make scoring easier. So an improved score is surely to be expected and -17 probably isn't even going to lead your section. St A's was about the only course without a par 5 but it was only three holes and I didn't have winds that strong.
Also if he can cheat why would he only do so in the showdown?