First, Nyman is a good reference and has always had some good stuff on pitching. I disagree with the basic premise because my experience has been just the opposite. My child was always the biggest kid around. One thing that stood out to college coaches is her size and ability to throw a ball. She was signed as an OF and ended up as a 1B. Don't count on her "flipping the ball" as mentioned in the article. She can flat out throw and led our area in assist two different years from the OF. One year she threw out 11 runners and her senior year she threw out 12.
As some of you know, I have had a lot of players go on to play college, pro and some MLB. I'd say that of the ones that made it to MLB, half at least were always one of the bigger kids. This article suggest that because players are bigger at an early age, they develop a lack competitive nature and drive. The article promotes the small gritty player who over came to get where he is. The world against him. It might be akin to the "fat and happy stereotype." I am reminded of one of a 7 footer I coached in basketball. After grueling practices, he would ask me to go to the upstairs running track and time him for a mile run. He set his goal to be sub 7 minutes on each run. While some of you might think 7 minutes is slow, you'd have to see what he did in practice and understand how dead his legs were at that moment. I told him he didn't need to do that and at 7 foot tall, he was going to play in college. He told me the perception is that 7 footers are slow and he wanted to stand out. IOWs break the stereotype.
BTW, a couple of Center fielders I coached became outstanding pitchers.