The red shirting goes on in sports where recruiting is done by high school graduating class, not birth year. It's a huge problem in football, and it's a serious problem in lacrosse, because it works. In physical contact sports, an extra year of growth and strength is a huge advantage.
Red shirting has been going on academically as well, particularly with the rise of J/K. The parents with kids with June, July, August and September birthdays are at enrollment being increasingly told to wait a year, and put their kids in J/K so they will be the oldest in the class, as opposed to the youngest (like I was). The thought is that they'll be more socially and mentally ready for the coursework, which is being pushed at earlier ages (and the schools these days are all about performance and maintaining their high test scores). If the child is on the younger end and is struggling before going to middle school or (apparently from the article) even high school, the parents might get the same recommendation to repeat a year.