No ... all of those are just statistical variables. And it's still no where near the point.
Seriously. I ask questions - in that post. Those questions are the point. All this nonsense about statistics and sample sizes is not.
But never mind. Lets stick with the statistics then: There is no magic involved in player skill that isn't accounted for by statistics. If champ X beats Champ Y nine times out of ten - then that is the statistic. It doesn't fail to account for the last time where Y beat X.
If the calculations are correct, the sample size sufficent, and the research sensible, the predictions will be statistically correct.