Online I see the same thing, how to kill a game.  

They say hold the Xbox button, then quit.  There's no fucking option to quit.  Hold down Xbox button, there's only "Turn console off" and "Turn controller off."  So when my kid is done with Minecraft, for example, seems the only way to return to the home screen is to turn the console off, then turn it on again.

They aren't that fucking stupid that there isn't a better way, are they?  

Try "pressing" the xbox button instead of holding it. This should minimize the game in a window within your home screen.

From Xbox support:

1.In the game or app, press the Xbox button  on your controller. This will return you to Home.
2.Verify that the big application tile is highlighted, and then press the Menu button  on your controller.
3.Select Quit.

could have used this last night

LOL that's it.  I read hold somewhere, that stuck in my brain.