CBP can try to be more efficient by not taking any breaks and bringing a few officers in from the office area to clear passengers, but they can't just relax the border just to hasten the line.
I don't consider it relaxing the border to let Americans re-enter their country without questions once their passport has come back clear and they have been visually identified as the passport bearer. It serves no purpose to ask a multitude of questions, other than to slow down a line that is often slow enough to begin with. If a point of concern comes up during the passport scan, that is one thing. Going on a fishing expedition is another.