After creating a sales order with a specific mode of delivery and delivery terms, a purchase order is created from the sales order (no direct delivery, just a normal one). The purchase order takes the mode of delivery and delivery terms from the Sales order when it should be filled what has been defined at vendor level. Imagine a situation situation the end-customer has a Truck 3 days delivery mode/terms and this is copied to the purchase order when it makes no sense since the vendor is in a different continent and delivers in ship in 60 days.