Alright, I double checked and XB Live Gold is now GamePass Core.

So... that's half of my doubts cleared, but does this mean then that GamePass users get the game for free? Because that's the point of GamePass. It's gonna be so funny if XB users are also required to buy the game and expansions, though If I was PlayStation, I'd be telling everyone that they don't need PS+ to play the game on PlayStation.