Fairy tales were designed to impart life lessons along with being entertaining. Unlike today, where an extended period of adolescence is common, our forebears experienced a world that was much harsher, where the transition between childhood and adulthood occurred much more quickly and where mistakes were much more dangerous.
Historically developers have been specialist. In web development you were either front end or back end. You build your portion of an app and didn’t worry about the other areas. The idea behind being a T shaped developer is to have a broad base of knowledge and then dive deep into a few areas.