Inconsistency between 'direct path write temp' waits reported while job runs and contents of AWR rep

I am currently working on site with a customer who is using RAT (specifically SQL Performance Analyser) to identify any SQL statements which may perform less well after his planned database upgrade (from 9.2.0.8 to 11.2.0.3). When creating a tuning set from a (quite large) set of SQL trace files generated from the current 9i database we noticed that the session in which the SQL tuning set was being created spent considerable time waiting on 'direct path write temp'. (We reduced, but did not eliminate, this by increasing the setting of PGA_AGGREGATE_TARGET - however this is not the point of