Twenty years ago, I'm sure that faster equated to smoother. Today, I'm not so sure. If it does, I believe that it's more a function of the fact that a club with faster greens must have more money to spend on greens maintenance, so they can achieve smoother greens as well.
The problem with building flat greens and making them fast on new courses is that everybody demands fast speeds on old, undulating greens which can't handle them, and then follows the pressure to flatten out those old greens. If we'd just build more undulating greens on modern courses, then nobody would need them to be so fast.