When I pull the Workday Journal Lines report, the “Created By” field is populated with the name of the Approver, not the person who created the Payroll Accounting Adjustment. Why?

This is a nuanced way Workday pulls the data.  It replaces the Created By user with the Approver once that step has been completed in the Business Process.  If you want to find out who initiated the Payroll Accounting Adjustment, the better way of finding that information is by finding the Payroll Accounting Adjustment in the worker history and then navigating to the process tab.  This is detailed in this Quick Reference Guide: https://uvafinance.virginia.edu/resources/find-payroll-costing-allocation-details-worker-history-qrg