Why does the TR_BSP_LOAD Process Populate the Process Instance as 0 on BANK_STMT_TBL?

We are on 9.2 Image 33, PeopleTools 8.57. When loading a bank statement file, after the TR_BSP_LOAD process completes to success the PROCESS_INSTANCE field on the BANK_STMT_TBL record is populated with '0' (zero). Why would this process not populate that field with the Process Instance number of the TR_BSP_LOAD process that just loaded those transactions? Usually when a process completes it updates the record for the transactions it processed with the process instance number of that process. Is this functioning as designed? Is there a reason why it populates this way?