In Business rules there is a setting to require journal entry batches to be approved before they can be posted.  If this business rule is set, it will apply to Journal entry batches created in General Ledger, therefore those batches will have a value for the Approved by field.  Batches posted from Subledgers, like Accounts Payable, will have blank values for the Approved by field.

If you want to review batches posted from subledgers, restrict the security rights to post batches and validate the post prior to posting to the General Ledger.