why does 'Generate Shipment Request' program checking any type of reservation instead of On-hand

There are two scenarios where GSR doesn't check the onhand availability. As long as some type of reservation exists , it still pick release and drops it to WMS

1. Back to Back sales orders which creates the PO and reserves it against the sales order automatically. However PO receipt has not yet been performed and there is no inventory available for that item. But still 'GSR' program picks it up and drops it to 3PL
2. Similar to Back to Back. User creates the sales order and create the PO separately and he link both of them under manage reservation. Though PO was not received still GSR pick release that order and drops it to WMS