Abuse of sign on/sign off times is one of the more prevalent pressures applied to pilots, and one which regulators conveniently ignore by allowing unrealistic protocols in operations manuals.
How many Australian airlines still persist with 45 minutes before STD to 15 minutes after ATD as the 'approved' duty period? Most, I would guess.
If aircrew were to arrive at briefing precisely 45 minutes before STD, complete all their duties and clearance of security etc in a responsible but unhurried manner, the schedule would soon go to hell in a handbasket. On-time performance is a big deal for the marketing people.
As for the regulator, at audit time or during proving flights, simply timing the period for all pre-flight and post-flight duties to be completed could form the basis for legislating on an operator by operator basis. Those with better infrastructure and more efficient procedures would be less penalised than those without.