Whilst conformance has significantly reduced the occurrence of rogue no shows, there are still plenty of people who clear conformance and choose to miss their flight thereafter. Some people get sick, some people have changes of plans, some people decide to go through to enjoy the lounges before "disappearing" and we see many of those proudly saying so in this very forum.

Ultimately, a passenger clearing conformance is no reason to keep a gate open beyond its closing time, and again, doors were closed at 7.19 on that occasion, ie t-16 of the initial time. Indeed, if a passenger cleared security at t-50 and doesn't make it to A6 at t-20, the most probable explanation is that their plans have changed because from security to A6 takes about 2 minutes.