I have reached out to Shopify Support regarding this as well yesterday, but they just link me to their docs, so I think it will be difficult to find a solution to this specific issue..

Hey there, my company has integrated with Shopify and in the Get Order API, we have added the filters of:  financial_status: paid fulfillment_status: unfulfilled  However, the response from Shopify API still includes fulfilled orders. Wondering how t...