That movie is biased propaganda advocating a particular diet, not a proper scientific study. You can certainly cherry pick a few elite athletes who perform well on vegan diets, but the vast majority of elite athletes are omnivores. Ever some of the movie subjects ate certain animal products such as eggs.

If you search around a bit you'll also find numerous anecdotal reports from elite athletes who tried vegan diets and found that they seemed to have more difficulty recovering from injuries. There seem to be some subtle nutritional deficiencies which aren't fully captured in the USRDA. This issue is difficult to study in a rigorous, controlled way due to individual differences so we'll probably never get conclusive data one way or the other.