I can't help thinking that this particular incident was partially explained by the fact that instead of going to CCR, the OP's son went to (presumably) Galleries Club North, which is near to Flight Connection security. It would be unusual for someone to claim access there based off previous First travel, when CCR is fairly close by.

Had he gone to CCR I would expect a very different reaction, since a good third of people using it are in there off the back of their previous travel in First, rather than their onwards travel. So at the so-called Secret Door, if you have a boarding pass with First on it, I can't imagine any delay there at all. At the next checkpoint, the main reception desk they thenscan your onward travel boarding pass (and then make a note of the previous travel if it was on a separate PNR).