Note that Cottonwood's route involves several major climbs and descents, as well as a middle section through the San Luis Valley that is both high and flat.
Since he and I have both been able to achieve relatively low average consumption numbers on several long cross-country drives, I wonder how much it has to do with the high average altitude at which those trips were driven. My hypothesis is that torque sleep is ineffective above some power drain close to 30kW (these are all made-up numbers to make a point), and that because of the lower aero drag at a given speed at higher altitudes, driving 60 mph at altitude puts us in torque sleep a much higher percentage of the time than driving 60 mph at sea level. Since above the threshold it appears torque sleep cuts off pretty abruptly, you'd have to drive 50 mph (or whatever the real value is) to see the advantages, and very few people have the desire or discipline to drive that slowly on the open highway.
Like I said, it's just a hypothesis.