So why don't all airlines monitor performance?
Personal record with Emirates was 8 minutes from doors opened to in car on the way home. (albeit from First) On the flip side Monarch, cleared immigration within 15 minutes of doors open, (from row 15 of a 321) and then waited a further 55 minutes for luggage.
In the case of the latter, immigration wasn't a factor, purely down to poor baggage delivery.