I am not ignorant to the variations in Charizard X's movepools and strategies. Nevertheless, you must agree there is a standard for Charizard X; that being the offensive set heavily empowered by Dragon Dance. Regardless of that, I was in a mindset of broad generalization and you appear to be down in specifics.
Charizard X is a common threat used in "OU" and many players are well equipped to deal with it. I'm sure failed predictions have occurred on occasion due to variations in Charizard X's set or other factors, but as a principle OU players are more aware of strategies for defeating a common threat than an uncommon threat, or even an uncommon gimmick.