In my experience (and this is at a "top" school/program), this has not been the case at all. In fact, a lot of the types that already had prior experience seemed to struggle when it came to more difficult or theoretical/mathematically rigorous classes (e.g. Algorithms & data structures etc.). I suspect that a lot of those who had already programmed did a lot of little personal projects or hacks. Maybe they learned some different languages, played around on the command line, generally dabbled in different areas of CS and software, etc. But I think the kind of skills gained from doing these sorts of things are mostly trivial. The types of problems solved in most typical apps and websites are not that difficult technically. You learn about a lot of the difficult problems in software and computability through CS material. And the other difficult problems are engineering ones - things like necessarily complex systems with lots dependencies, large-scale or scalable systems, software with high technical demands, comprehensive testing etc. etc. But that kind of thing is learned on the job, or at least in some kind of capable team working on an important project. Not by writing little scripts or apps on your own. Learning how to write readable, modularized code can be naturally (and fairly quickly) learned in intro classes if you are mindful and dedicated to improving.

However, this is just my own experience and observations. And there is no doubt that there are plenty of people out there who started at a young age, and are also superb at computer science and/or are fantastic engineers. But I don't think that in itself is a great predictor of someone's capability.