The security checks that you "see" being done at the checkpoint are but one of many that every crew member must go through before boarding an aircraft.

Those crew members that carry firearms go through even more, and are issued credentials that identify them to the TSA as well as ground / terminal airline personnel. And that is not the only ID they must have before boarding an aircraft. So yes, we know who they are before we allow them access to the sterile area.

I don't like the whole crew cutting line thing myself. They are the true professional flyers, and as such they should be prepared for whatever the checkpoint has to throw at them. Arriving 2 hours early, clearing security in a timely manner, and bringing only those things allowed in their carry-on's. These are just a few of the things that crew members "should" be responsible for in addition to whatever requirements there may be for their flight duties. But no one asked my opinion when they made up the rules.