Your bill reviewers get the supplier invoice and any mismatches together before they decide what to approve.
Your reviewers see what changed since the last approval and get the revised order for a fresh decision.
Your requesters know what to add to their original purchase forms, while the approval waits for a reviewer.
Your approver sees the purchase order link and line differences on the bill before making a decision.
Your AP reviewer sees a possible duplicate and its earlier invoice before approval or payment.
Your requester knows exactly what to add, and your approver can see why the bill is waiting.