No, if it's a flow issue of any kind, it's usually a waterflow issue, because at highway speeds there's usually plenty of airflow through the rad by the forward motion of the car
That's the point that at highway speeds there should be sufficient air flow to cool.
BUT...
if the air flow is restricted for some reason -fans in the way, shroud, massive leaky air seals, blocked fins - then there WOULD be an airflow issue.