I don't think culture is directly relevant to Indy's teaching a game when he could have learned one. Had he been an Indian hero of the same type, he would likely have taught American cricket, not learned baseball. (The exception, of course, is the case in which the hero learns the other culture's game and excells at it almost unreasonably.)
In a transformative arc, his learning their game out of interest and consideration would have been normal and expected - the point of the story is for the hero to learn, grow, and change. But in a relevatory arc, the story's purpose is to reveal and demonstrate the hero's excellence - how they and the virtues they represent are just what's needed to solve the story's problems. (Captain Kirk in the new Star Trek is this type of relevatory hero, as was Luke Skywalker in Star Wars.)
