That might be true for Purchase Requests, but not for Requisitions - the former is meant for Employee Center users to enter, and is basically just a different "status" of the Purchase Order record type. Requisitions, on the other hand, are a completely separate record type, and are only available if you've purchase the Advanced Procurement module from NetSuite. Requisitions let you enter lines that you might source from multiple different vendors. From a Requisition, you can generate one or more POs through a bulk creation process/screen.