Hmmm
I don't know if it is always the wrong thing to pitch a kid in that situation. Yes, if a kid throws the curve too soon or pitches too many innings they will likely have arm problems when they are pitching later in their careers.
But in a case where there is no career, and perhaps the instance that is being examined is "the career" for the pitcher. This kid is apparently not going to pitch in college or as Playball said only one more year. If that is the case he need not worry about what happens down the road in a few years.
It's kind of like the argument over whether a 12 year old should throw a spinner curveball to win the championship because he can't get the fastball over 50 MPH. I'm not so sure you need to be worrying too much about whether or not his arm will hold up when he is 24. He won't be pitching when he is 24, probably not when he is 15. Yes if you are a legitmate prospect or your intent is to play as long as possible you need to conform to these standards, they are proven.
I think that most forget that the vast majority of these players are not going on to some higher level where they would regret having thrown 145 pitches in a game. Again, it sounds likely that (by choice) that this could well be the highlight of this pitcher's career. Food for thought.