In reply to Kyler Phillips.

Hi Kyler,
the resolution is limited by the real screen resolution: I have the same 1280x720 as my maximum HiDPI one, since my screen is 2560x1440 (so width and height are both 2x).
The "simulated" resolutions available on real Retina Macs are not available with regular screens, and I think it's due to the fact that they would be pretty fuzzy on lower res displays.