At some speed, driving fast on the highway will eventually be less efficient than driving in very bad gridlock. It isn't entirely unreasonable to incorrectly estimate the intersection of two causes of inefficiency in driving.
It's probably possible to design a car so aerodynamically inefficient at 35+ mph that stop and go is preferable to cruising at even moderate speeds.
...although it should be noted that the Model S has the second best drag coefficient on the market today (it was the first before a new Benz was released in 2013):
