We currently do not use this function in Sage but, we are looking more into it. One quirk I am finding is when you select the "use back ordered quantity" as an option, the report created includes lines that do not have a back order quantity. This follows the Sage logic in the Help article, "Select this check box to use the sales order back-ordered quantity as the ordered quantity on the purchase order. Clear this check box if you do not want to use the back-ordered quantity. This field is available only if Sales Order Quantity is selected in the Base Order Quantity On field and it applies only when the back-ordered quantity is greater than zero."
I am struggling to figure out the why of this, I am thinking if the line doesn't have a backorder quantity then there is enough on hand inventory to fullfill the line, so it shouldn't include this quantity on the PO, has anyone else found a way around this?