https://wccftech.com/xbox-one-x-pubg-downgrade-patch-deployed/

Bluehole and Microsoft are rolling out the Xbox One X PUBG downgrade patch in order to increase the game’s performance on Microsoft’s enhanced Xbox One console.

As covered yesterday, the downgrade is temporary until Bluehole finds a way to stabilize the game’s performance without toning down its graphical options on the One X. The nerf only affects shadowing and reflection in the game, and Bluehole has assured that textures and resolution remain the same.