I don't think the win rate can be direct proof of cheating. For many, this percentage does not reflect their actual skill...

If you read the discussion about the signs of cheating carefully, you will see that it mentions a high win rate in games against top players. Many know how to inflate their rating by playing against average players and suggesting starting a new game if the position in a postponed game is unfavorable. And no one would think to criticize the percentages in that case.
Ms. Smekhova, thanks to her skill (and, as some believe, luck), also has a very high win rate in the games she has played. At the same time, Alex himself writes that if he played against Forrest, Mizraeel, Pete, and Lebron, he would have considered a 65% win rate to be good.