There's nothing forbidding it, but it ups your chances of not getting selected. Someone explained further up in the thread that your itinerary is given a risk index and if it's too high, no precheck for you.

Just as a datapoint, I'm a GE member and I've never missed a precheck screen at DFW (~15 flights so far this year). None of them have been 1-way, but judging from the stats in this thread, GE gives you a pretty huge boost.