Is there any way to query Coupang's discretionary-cancellation or quick-refund orders?

There is no separate way to query discretionary-cancellation or quick-refund orders specifically. 

However, you can use the [Query Return/Cancel Request List] API to see if an order that was cancelled or returned was a discretionary cancellation or a quick refund. 

Find out by checking the following attributes in the json data query. 

For more details, please refer to the [Query Return/Cancel Request List] document. 

Going forward, orders that are cancelled while in 'Product in Preparation' status are refunded immediately. 
Even if you see "completeConfirmType=CS_CONFIRM", "cancelCompleteUser=3P_CACNEL" indicates that the order has been cancelled by the Customer while in 'Product in Preparation' status.