Come on, you aren't that stiff. The first (modern) olympics didn't have all the sports they have these days, either, and had others not present now. I imagine 50 years from now something might have changed as well. Obviously these mages have the kind of activity that suit mages. They aren't normal athletes so it would be stupid to make them compete (only) in the kind of events familiar to us. Also, olympics have lots of shooting sports. In the first place I mentioned winter olympics only to demonstrate how big sport events have the athletes themselves and then the background support personnel, because that's exactly what we have here as well.

The surfboard race isn't out of place at all in my opinion. Even if the events in general were reflecting some skills of military potential, it's still not so weird, especially in a place like Japan with lots of water. Especially when nobody but Tatsuya ever invested two thoughts in flying. Grab a piece of whatever and cross water at high speed. Seems handy.