From what I have seen down here, Deer take to sorghum okay when it first comes up but dont care for it as much when it matures. Its great for doves and turkeys but not the biggest draw to deer unless there isnt much else in the area.
Hope it works out for you.
Unless they have mixed some legumes in with it, the protien levels probally wont be high enough to make a difference. They probally mixed some summer wheat and/or oats with the sorghum. Thats probally whats attracting the deer more than the sorghum.