There are some twelve-year-olds who are grown men, six feet tall and 165 pounds of muscle and fully stocked with hormones. But some of them are still children. My boy is 12, light-boned, and still a child in his body, his emotions, and his interests. The boy who went missing looked in his photos as if he were the same type.
The article says 5'4", 110. Same size as my Bill (and me, if I skip supper tonight.)
It's true that there's a considerable variance in maturity among boys who are the same age and the same size. In fact, there's often a considerable variance in maturity in the same boy on the same day!
I think this story (assuming the MSM info is more or less true) illustrates this point very well. On the one hand, the young man took off on his own and ignored (or hadn't been taught, or hadn't been reminded lately) the basic "what to do if you're lost" rules. On the other hand, he made it through three days in the woods in pretty good shape, so his training and instinct kicked in at some point.
Hopefully he will draw the right conclusions from his experience. ("Breaking rules and doing foolish things gets a lot of attention!" is not the right conclusion.)
At 12 I was 6 feet tall with a 10EE shoe size, but only 112 lbs. A year earlier I had been 4' 9" with a size 6 shoe. It was a tough year keeping up with clothing.