I doubt it would make that much difference. Until the sweet 16, 1 seeds have a very high probability of winning. So do 2 and 3 seeds in the first round. After that, I don't think odds weighting would have much impact. I could buy quadrillion range, but 90 trillion is 5 orders of magnitude less than 9 quadrillion.
For instance, let's suppose all 1-16 matchups are 1 seed wins -- just take them out of the bracket entirely. That would have an order of magnitude effect, not 5.
Edit: if they were equal weighting the games, the odds of a perfect bracket would be 147 quintillion. So the 9 quintillion number is a step down, so it's applying some sort of weighting.