Of course, the proffered reason is that a flight crew member could have been compromised into taking a WEI through the checkpoint and then handing it off to a "terrorist" to take on a flight different from that crew member.

If more of these secondaries happen to crew members, then the TSA won't have as much time to do it to passengers and perhaps the unions and airlines will complain more and raise the level of discourse about ineffective screening. But then again, when their voices are heard, the TSA will probably go back to its old ways of just doing secondaries on passengers.