The EDeviceScreenOrientation landscape values appear to be inverted on iOS based on the comments in the code.
However when looking at how the iOS device orientation maps to the unreal EDeviceScreenOrientation in IOSPlatformMisc::ConvertFromUIInterfaceOrientation we find
The apple documentation for UIInterfaceOrientationLandscapeRight states "The device is in landscape mode, with the device upright and the Home button on the right." [Link Removed]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-95179 in the post.