'Generate PO From Sales Order' function and 'deliveryviarule' field inconsistencies

For example, if we create a Sales Order with Delivery Via (deliveryviarule) set to 'Shipper', then we use that SO to create a PO (by 'Generate PO From Sales Order' function), then we see that the PO now has its deliveryviarule field set to 'Pickup'. It seems like this should instead carry over the deliveryviarule value from the SO to the PO, and I wonder if just some code should be added to the OrderPOCreate class to make this happen, or if there was a business reason to not do so...?