Is there a reason all the scenegraph samples removed the option to press Up to exit the screen? For those users used to pressing Up with SDK1, would it cause a channel to be rejected if we included that in addition to supporting the all-popular back button for scenegraph channels?
No, i see no reason to reject channel for that - nor would i ask for permission if i wanted to do this particular one 
To me supporting “Up” to exit makes no sense since all remotes for quite a few years now have a “back” button - in fact i don’t think there is a Roku model that can play RSG channels and came with non-Back-ed remote. But if “Up” to exit does not create confusion in your navigation flow - sure thing, add it as a silent alternative to Back?
Just for consistency - and the back button is a further stretch of the thumb… 
We can’t have our users burning the extra calorie to press back when they can press up.
