Approval Framework in 9.1 not resetting PO status back to "open" when reducing the PO total amount v

We're having an issue with the Approval Framework in 9.1 involving situations where the PO total amount is being reduced via a change order.  When creating a change that reduces the PO amount after the PO has been dispatched, the approval status is being reset to "pending approval" and the user has no way to manually restart process.  What we would expect to see is the approval status reset to "open" the same way it does when a PO amount is being increased. 

We've identified a temporary workaround where the buyer first increases the PO amount, saves the PO, and then exits the record.  Then, they go back into the PO, change the price again to the desired reduced amount, and save the PO one more time.  This successfully resets the status back to "open" so they can then dispatch the PO.