Repro steps:
1. Open project "screen resolution.zip";
2. Build it to Win Store Apps;
3. Open solution and in Package.appxmanifest mark "Landscape" and "Landscape-flipped" supported resolution.
4. Tablet must be locked on portrait orientation. Deploy project to tablet.
5. Application deployed in "Landscape" mode. Now try to flip the tablet to "Landscape left" orientation. Application doesn't change its orientation.

Reproducible on 4.5.0b3, on Surface RT (win8.1) and Surface Pro2 (win8.1)