nik nak,
Please read my earlier post - I checked the SSR MODE C on climbout, when the A/C is passing an altitude.
This is a check a check to ensure that the airborne equipment is functioning correctly, NOT a check that the correct pressure is set as you have stated (how could we tell a one millibar mistake when our tolereances are +/- 200' (6 and a bit millibars)?
Fair enough, when in level flight, if the SSR indicates a variance of greater than 200' we check the pilot is flying level and if so, that the correct pressure is set, but that is not why we check SSR initially.
These A/C were validated and verified, the pilot error came in when the outbound pilot, when instructed to climb to FL100 (the climb given whilst he was still climbing on the SID), climbe to 10000' because he had the QNH still on the altimeter, instead of the SAS.
You have a valid point in saying that is should only be used on ATIS for lower pressures - one or two millibars will never be noticed by us anyway.