Sorry Chris I do not know where you get your 'facts' from, but once you get to marathon length endurance events many other factors become significant.

I agree that for circa 10 kmto half marathon events then ability to take up oxygen and use it is critically important, but once you get to distances above that then this is not the case - here other fatigue mechanisms plus ability to take in and use substrates etc are critical

But with your background you would know that or another blind spot?