Detect Hardware vs OnScreen navigation buttons

I’m trying to detect whether the device has hardware or on screen navigation buttons (back, start, home). On my test Nokia 635 device the monogame screen has the nav buttons overlapped at the bottom. whereas on my test Nokia 820 device the nav buttons are not part of the screen (dedicated hardware buttons) - see screen shot.

So far I have not found a solution. And all the articles point to an API that does not exist in the Monogame libs (Microsoft.Phone.Info.DeviceExtendedProperties).

Does anyone know how to detect if the device screen will have a nav bar at the bottom?

P.S. I have set the Preferred Height/Width and checked all other height/width properties between the devices and they are the same!

Some further information. My code works fine in all of the Windows Phone 8.1 emulators and Windows 8.1 emulators!

Could this be an issue with the 635 device?