Has nothing to do with apron level. Given current baro pressure reported on ADIS is used to determine if an altimiter is out of tolerance. I guess you may have a bit of a point at high altitude airports but usually a split is the main indicator there may be a problem.
Maintanence would usually have to do a scale check, sometimes this is done at just a few altitudes based off of 29.92, for certification I have had in the past to perform a check roughly every 2-3k feet up to 41k. The deviation allowed is much greater at higher altitudes and a split at lower altitudes is often just fine at higher ones.