One artifact of the need to provide real first and second-line support for the game is that the tech support and sustaining engineers have to have equipment corresponding to the minimum and recommended levels. It doesn't do to say "OK, we're going to support Core 2 Quad. Oh, wait a minute, we don't have any Core 2 Quad desktops anymore."
So these levels have to be stated in terms of equipment that the engineers actually have and can use. Hell, even Sandy Bridge systems are becoming scarce, and they'll be using three-year-old computers to do support at the minimum level. Maybe they still have an old Phenom II desktop they can use.
Even so, the omission of nVidia Fermi (4xx, 5xx) and AMD VLIW (5xxx, 6xxx) GPUs is odd.