I’m not sure I understand well your question, because I guess you are using the terms discontinuation and discontinued interchangeably. A discontinuation order is the order that was placed to discontinue an active order and its action is set to DISCONTINUE, a discontinued order is an order that has been discontinued and typically its action will be set to NEW or REVISE. With that said, discontinuation orders should never be returned in any list except if you call that special getOrders method intended for migration purposes.
An order that was discontinued would typically have a discontinuation or revision order pointing to it as the previous order where as an order that was completed wouldn’t.