I read it and didn't see a single thing about downflow or crossflow. Did I miss anything?

In general if the radiator is a single pass heat exchanger it doesn't really matter what direction the tubes run. I believe that radiators had vertical tubes because they fit in the grilles better and could have the radiator cap at the top where it was most easily accessed. When Detroit went to the "longer, lower, wider" mentality the radiators became lower and wider to fit under the hoods, thus the crossflow radiator.

R.