little note:
Steam still not need Gaming Services, but of course the Xbox app to login.
Also in windows 11 are Gameing Services not necessarly needed to install ( also if these xbox app annoying with the message ) 
@PilotOccifer
The content , e.g. the mentioned G1000, will be updated within the in-game Content Manager and initial installed over the marketplace. One time installed, it also notify about existing updates. I can currently not give screenshots and only mentione what I have in mind: open the content manager ( or click on the notification icon if there is a update-message ) , then you should see the packages for which update exist. Choose select all and then “install”.