I probably have a repro case on an iPhone X over here. In landscape mode it is still possible to swipe from the top downward to slide down the iOS notification screen. Likewise swiping from bottom upward will minimise the app.
There seems to be dead-zones for beginning any touch inputs as well on these areas. If a touch input begins outside these areas the input will register inside these dead zones. However no touch input that began inside these dead zones will register anywhere.
Added ticket DEF-3196 for this issue.
One possible fix might be to use preferredScreenEdgesDeferringSystemGestures. I have not verified that this resolves the issue though.