What is 'Xbox One X performance'? The thing is not out yet, we don't know how it performs and we don't have any actual data to evaluate its performance
True, it isn't out yet, but early indications are amazing. Just what was shown of Anthem alone already looks amazing, and appears to be legit. Alpha build, apparently checkerboarding to 4K, but when it looks like that, I'm honestly hard pressed to complain about how they're doing what they're doing.
Assassin's Creed Origins, the game I personally played the most at E3 on actual Xbox One X hardware, looks every bit as good and as convincing as any high end PC title I've seen. If the Xbox One X didn't exist, everybody would believe it was running on some expensive, tricked out PC.
And even though it was the dev kit and not the actual retail system, the dev present said it was totally representative of how it will run on retail kit, and that it's likely to end up better due to the fact that the game is still just in the alpha stage with much left to be done, on top of the fact that Microsoft are still making improvements to the development kit.
It's not just a resolution thing with the X, though. The overall visual impressiveness is something to behold. These streams aren't doing many of these games any justice. They look so much better in the flesh.