Honestly, not much to think about. DH strategies vary by Coach depending on the makeup of his team. In high school some of the best athletes are pitchers, so they typically hit for themselves which gives the Coach some options offensively and defensively.
Your friend's Coach elected to play a better fielder in the field (not hit) and send a better hitter (DH...not play the field) to the plate in an attempt to win the game. High school coaches do this all the time, as they want their best 9 glove defenders in the field and their best 9 hitters at the plate.