PO Approval with different line types

Using 9.2.  Is it safe to say that for any line types that are on a PO with an approval route, there needs to also be order activity rules that support the statuses in the P43081 processing options? (waiting/approved/rejected)

We have been getting in trouble because we have this scenario:

3 lines on a PO

PO gets approved

1 line gets received and the supplier invoices us for it

AP user vouchers that one line and add additional charges with a J line type that goes in at 400-999

Buyer user needs to make a change on line 2, which sends it back through approval, rightfully so.