I had an update to an app I've had in the Microsoft Store since last fall rejected because the display was "truncated" in portrait mode. It's actually not "truncated" just squeezed as it is intended to be used on desktop, notebooks and tablets but not phones. Someone got aggressive testing and tried running on a couple of Lumia Windows 10 phones (I didn't know those still were being sold). Is there a way of locking down landscape so it can squeeze on portrait? I can do this on Android and iOS. It seems to be a reported bug too:
Most of my users will be using the app on desktop not a phone since they either use Android or iOS on mobile for this app.