I'm going to do some more research and write up a post on this.
One thing I would like to mention for the moment is that people do find these strategies by themselves. Yes, there is also a collaborative effort across different games to pool together the best strategies, but there are some people who find a lot of stuff by themselves and then share that information. I think everyone who is capable of playing Mario Kart is also capable of finding a skip by themselves if they keep attempting different strategies and learning how the game mechanics work. AI does not glitch hunt, at all, but any human can.
Edit: I would also point a couple of other things out. The strategies used by fighter pilots do not come from the individual either. These techniques have been pooled together over decades. If you consider this, you could argue that the individual is actually more important in MK64 in relation to finding skips and whatnot.
I think another point to consider is that AI has a natural advantage over humans in any kind of combat situation. AI has a completely different idea of what risk management is when it comes to something that is life threatening. This exercise was a simulation, but the experience and training of a fighter pilot is always going to be based around staying alive as the most important priority, and that is still a factor even in this exercise.
Just a couple of points that I feel need to be said:
People don't discover the long range strategies unassisted either. Once one person comes up with a breakthrough that information is available to everyone else. Everyone else copies and optimises it. I think you're suggesting pitting one AI against all players, rather than one AI system versus the realistic performance of one human. I wouldn't be surprised if an AI could outperform the entirety of humanity starting from scratch with zero help anyway, but that is a different test.
One would reasonably expect significantly more resources and motivation to apply to a military application like fighter pilot training (and making fighter pilots necessarily redundant) than to playing Mario Kart. When I say 'limited resources and motivation' I mean relative to a research goal that's actually useful.