This looks incorrect based on Denver's graph. The post claims its effectively 100% along cardinal directions but thats obviously not the case. All of downtown is NE/SW.
(Maybe Denver is including a lot of urban sprawl?)
The downtown Denver grid was aligned parallel or perpendicular to the approximate course of the South Platte River there. It covers a small area--I recall it as something under a square mile. However, I would never say "effectively 100%" along cardinal directions, for a lot of places one might want to go are in downtown.