skwinty,
This is a good point to check out. Naturally any adjustment will make a difference to what the pilot will see. However in the case at hand we are using the pressure data in the FDR file. There are 12 flights on the file and in no case is there a step in the pressure, either in ascent or descent. We can assume therefore that this is unadjusted data and will give correct True altitude when adjusted using the known baro and temp at the location on the day.