Exactly, I have '72 Scamp with a 318 and a stock clutch fan. It runs great at about 185… no problem. I had '50 Buick with a 455 Buick engine and dual electric fans and puked coolant all the time from overheating. Bottom line for me is it was never engineered that way. So if does work for you, you got lucky. Also, one of my vehicles, I don't remember which, overheated on the freeway and the cause was rusty fins on the radiator that would fold shut at higher speeds. Your radiator is new so I would suspect there's to much stuff hanging on it to let enough air through it. Fans and a restrictive shroud maybe?
