To date, my travel has been exclusively domestic, so I do not have any experience with Customs. IMHO, security screening for American citizens should be very brief - a fringe benefit of being an American. Citizenship proved by passport.

As far as domestic flights, reverse gate screening has to be the most asinine policy from an agency that has promulgated and impleted quite a few asinine policies. "Closing the barn door after the horse has escaped" is a rather mild description. If one has a connecting flight, then like Bart said, back through main security checkpoint. If one has reached one's destination, then let the person go. Isn't the objective to make sure that nothing prohibited gets onto the plane? Once the passenger is off the plane, TSA's mission is supposed to be over. Or is this mission creep, toward an airport and environs law enforcement agency?