Again, you are missing the point, just because something is "likely" to happen doesn't mean it did happen.
What you are basically asking is that we should provide a "negative proof", imagine me going through all the pro matches to prove my point that it did not happen (going in this extreme) when you can just show me a proof that it did happen.
It's you who's missing the point. You're engaging in ridiculous pedantry over whether or not people cheat in a very popular video game, take a break.
The reality is that it really couldn't matter less whether or not anyone has ever cheated in overwatch pro games, but we can pretty safely assume that somebody has.
Is this a topic that genuinely calls for greater precision than this? What's the benefit?