I’m a lazy guy that is part of one of those elite gyms (kind of by accident, but it is what it is). As a result I get to see what actual elite athletes eat by virtue of being around that and I can assure you that these elite sports champions are not eating any form of cereal at all as part of their daily regimen.
I was a borderline elite athlete at one point, training with actual elite athletes. Most of what we ate would be considered a "wildly unbalanced diet", and when we were competing it was just large volumes of calorie dense food, be it pasta, protein bars or milk.