In that sense in a way it seems like you have already been penalized by not getting the information available in the status bar. But it seems like that was by design to maximize the space available to apps in landscape. So accordingly it sounds like anything that would show up in the status bar wouldn't appear in that orientation, since the back link is part of the status bar essentially (or at least is worked into it so that it doesn't take up any app space) it seems that it is within the design that it doesn't appear in landscape as there would be no place to put it without introducing on the app itself.
One the one hand I see what you are talking about, on the other hand for those who are using landscape mode at least partially for the reason of having a "full screen" experience could find it in bad taste if Apple did somehow add that in there taking up that "full screen" space (as if they would have added the status bar to it).
That said, perhaps they could find some less intrusive way of doing it, which can work so that it could be used and not feel intrusive in that "full screen" landscape experience.
