Xbox game pass ultimate mobile cloud gaming is amazing except for 1 minor flaw and thats...

No you cannot, except through the cloud with an Xbox game pass ultimate subscription.

I am accepted in the game stream preview, but I was not streaming at the time of using the game pass mobile app. Its the game pass app itself that is lagging. I even logeed out of everything except the game pass mobile app on google play store. I had all
xbox apps on my phone uninstalled as well, except the game pass mobile app. I am a part of Project XCloud if thats what you're asking.

My question was not devices cloud gaming supports. It was whether the Game Pass Ultimate subscription covers a game on mobile phones as well as other cloud platforms. The link you referenced does not address it.

No. Currently you can only play cloud games while they're included with Game Pass Ultimate (with the exception of Fortnite).

Game Pass is like Netflix for games. You can play any game in the library without purchasing the games individually. There is a Game Pass for console and a Game Pass for PC.

Game Pass Ultimate includes both Game Pass for console and Game Pass for PC as well as a Gold subscription so you can play online multiplayer. Ultimate also gives you access to Cloud gaming and EA Play.

Xbox Cloud gaming allows you to sign into a laptop, mobile device, and the console, and play games without having to download them.