So there isn't "zero" airflow through the fans on the freeway. That's completely untrue.
But the fan may be limiting the airflow more than it's improving it, the turbulence of the spinning blades can reduce airflow. And if the air speed coming into the fan is too high it can lower the fans efficiency too.
If the engine wants to run at 195° on the freeway, that's absolutely fine. Like I said, the stock 6.4 doesn't even open the thermostat until 203° which means it's ALWAYS running hotter than that once it's past warm up, and on those engines that means anything past a few minutes of run time. Turn the fans on at 205° and off at 200°, I bet it still runs 195° on the freeway.
Why? Lots of really smart people designed that engine to run at 203° or above. Maybe if you wanted absolute max power for a short time (ie, a drag race) you'd want it cooler than that. But if you're just driving around town, on the freeway etc, it's going to be better for the engine to run it at the temperature it was designed to.
