Steps to reproduce:

1. Open attached project
2. Switch to iOS and make sure 'Target SDK' is set to 'Simulator SDK' in player settings
3. Make a build
4. Open the build with Xcode and build to any iOS simulator
5. Notice the DeviceGeneration returns 'Unknown' regardless of which simulator was chosen (reported in the text field in the middle of the screen)

Note:
Works correctly on actual devices.

Reproduced with:
2017.4.1f1, 2018.1.0f1, 2018.2.0b1