if there was more room around the capitol, my guess is that they would have built like that.
Of course. WOA has already said that. And they were careful not to build cities between the two cores because rank corruption would destroy the second one.
Actually I think that WOA's map on this thread is a poor example of optimal FP placement. The best choice would be city 15. However, city 6 is much more productive so, in order to get it up in a reasonable timeframe, he chose that instead.