Users report issue with system not withdrawing/reissuing approval notifications for invoice changes

A user has reported an issue where the system is not withdrawing and reissuing invoice approval notifications when invoice lines are cancelled and re-matched to a PO. She believes that the system should automatically withdraw an approval notification when she cancels an invoice line/lines, and then reissue a new approval notification when she re-matches the invoice lines to the PO. Does anyone know if this is a genuine system issue, or expected system behavior? Does this have to be manually withdrawn/reissued by a user, or should the system automatically do it? Appreciate any help!