I don't necessarily see that this is particularly relevant. The point of a PhD is surely to show that a student is capable of performing at the very peak of their field. The well-roundedness should come later, and just like an undergraduate degree is not "Job Training" and postgraduate one doesn't instantly make you a leading scientist.

Also, from what I saw of other students doing PhD's in the US, they already take several years longer than us in Europe because of the lack of specialisation in undergraduate degrees - they spend the first few years in effect "Catching up".