I think you may have hit the nail on the head for this. I think that if the QP isn't full or crowded, then they merely let the other members in so long as it appears that they have a boarding card. If the club is crowded then they would resort to the BP checking in detail. My observations are limited, and therefore, not fully representative of what may happen.

When I used the SYD QP it was on a Sunday morning. The club was fairly empty. Simply walked up to the matron showed my QC card (with a boarding pass behind it) at a distance that I am not sure she could even read the expiry date on it, let alone the BP.

However on my return from CNS on a Thursday the QP in CNS did look at the boarding pass along with the card. However, they did not scan it or otherwise make a note of it that I saw. It was much harder this time to actually find a space to sit in this club. This it would seem indicates that there is a tendency to enforce the rule when the club is crowded, but not when it is empty.

QF WP you are right I would be doing so at my own peril. I am not actually suggesting doing it. It was more of a mindless wandering of my own thoughts. It would however (if the club were empty, i.e. the matrons aren't really checking), eliminate much of the need to play escalator roulette around the QP for the WPs present. Of course as you said you love a challenge.

Which brings me to another point, that is probably more appropriate for the QF board, but anyway. What is the point of QF denying paid QC members access to the club if they are not flying, but granting that ability to WP? I can understand denying it to lower level members who have not paid for access, but I would think if you paid for the acess then you should get it even if you are not flying. (that is the way the clubs work here in the US, if you can get past the security)