Changing an Approved Requisition after a PO has been created

Summary

When an approved Requisition is updated (added more funds), it triggers a change order to the PO. Is the Requisition re-routed to the approvers?

Content

I am testing a PR that was approved and converted to a PO. When a change is initiated against the approved PR by the requester, the requisition triggers a PO change order. Once the PO Change is approved, the PO amount is updated with the new amount while the PR still shows the original amount. Is this the expected behavior? Can we re-trigger the PR approvals since the new amount is higher?

Thanks! 

Siva