He has already learned his lesson
I agree with the principle of charging for rescues for people who are negligent. I was hoping they would stick to the numerous clear cut cases of negligence. I'm not sure if this one fits the bill. He chose an overly ambitious hike for the season and one would only know this from experience. He was young and made some good decisions while he was out there, turning back at high stream crossings, finding shelter. He was hiking to safety when found.
I went for my first hike at 14, a 3 day on the AT in CT. My Friends and I knew that if you followed the white blazes you could make it to Maine. We hiked in jeans without tents, stoves, water treatment, or maps. This was in 78 when parents let kids take some chances. We learned alot on the first trip and went back every year until we were 18 and made it to Moosilauke in NH. We were lucky our training ground was much more forgiving than his. I guess we were negligent with a good outcome.
Maybe they are fining him because this was an expensive rescue instead of focusing on whether this was actually gross negligence