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?