Another possibility is that the app requires the GDR 2/Amber update. In that case, since that update comes out of the box on the Nokia Lumia 925, it should work on that phone. A third possibility is that the app is being rolled out in waves. If you're a Nokia Lumia owner and have been able to download the app, let us know by dropping us a comment in the box below.
source: YouTubeUpload, MobilityDigest via WMPoweruser