We really do like to argue here, don't we?
I think the point is that all other things being equal, greens where the ball can easily get away from you leads to more putts and more time. As Joe B pointed out, that's just not putting but chipping and pitching and bunker shots, as well.
One might argue that the same effect may occur on highly undulating greens that are slower simply because of the degree of challenge/break, etc., but at least that's fun.
I'm not sure watching a barely tapped putt continue to slide 2, 3, 6 feet past is really all that enjoyable.