Does This Debunk the "Coolant Can Flow Through the Radiator Too Fast" Idea???

I have another example. Kenny at Indy built my 499, 830 hp. When I first got it in car it would peak at 240 degrees going down track. Belt driven water pump into a VW Scroroco radiator with external fan. I called Ken on this and said that’s fine, those heads have to run hot to make the power-heat, heat dissipation. He said I’d loose a lot of power running them cold (180). Anyway I didn’t like it being that hot so I put the correct factory shroud-fans on and a 160 stat, it ran that temp idling all day, lost about a tenth of ET in eight mile. Went from 5.60 to 5.71.
This is real world stuff not something read off the internet.