This is a need.The approval workflow enters a status from which you can not exit without manipulating the data if you answer "No" to the question if you want to create the customer.The workflow is then approved, but the document still has the status "Approval Pending."
There are several ideas regarding this issue, I can add link, so this is the header for the ideas: Add Posted Sales Invoices into Intercompany Management, Request for Intercompany Digital Attachment Enhancement in Business Centra, Automated invoice transfer between Intercompany.