However, the New Republic article was more about technology entrepreneurs who aren't necessarily coders or engineers in the traditional sense.
These entrepreneurs and the VCs who seek them out and fund them tend to have a bias toward youth, because there have been some stunning success stories among the young, as laid out in the article and in many comments here (Torvalds, Wozniak, etc.).
But, the skeptics interviewed in the article argue that these 20-something wunderkinden are the edge cases, not the mainstream. Historically, scientists and technologists have tended to accomplish more in their 30s and 40s and beyond.
In the world of software development, certainly there is a mixture of talent across the age spectrum. There are excellent programmers in their teens and twenties, and mediocre coders in their fifties. But there's a general consensus that experienced programmers in their fifties are better able to avoid some classes of mistakes that twenty-something coders simply haven't had a chance to see yet (but will).