The discussion on approach gates is incomplete. The concept of a gate defines a position during the approach where specific conditions should be met, e.g. flight path accuracy, speed, configuration, power.
An industry standard is that the maximum speed deviation is Vref +15 (FSF ALAR Tool Kit), aiming for the target approach speed (Vref + additions). Boeing recommendations appear to differ form this norm, most documents quote Vref+20.
Thus, operators following this advice might be expected to decelerate during the approach – the crew expect to see speed decreasing and the thrust levers moving aft under autothrottle control; in this accident to a degree, normal indications.
So suggesting that use of an approach gate might have prevented this accident might not be so certain. Indeed if the crew had met a ‘perfect’ gate check, the RA malfunction, the human weaknesses, and subsequent events could still have progressed to an accident.