Incorrect.
Your fan would have to pass over every sq in of core for that to be accurate.
That's what the shroud does though, it's funneling the air through the entire core to the fan's draw.
Your fan (and mine) only draw air through the fan blades swept area.
Some combos will need a shroud to keep cool, some wont.
It's not "run it close and you won't need a shroud".
I fit one to my app. but haven't needed it.
