You are correct.
However, you can set up files to generate serial numbers on being saved to the Vault through the EPDM Vault View and / or SolidWorks or by setting up EPDM Templates to create the SolidWorks files. Then you can use the serial number in the Dispatch script. Unfortunately, when you copy a file using Dispatch it will not generate a serial number.
We decided NOT to auto generate Serial numbers but to assign them using an Add-In (the only Add-In we use). We have a Dispatch script to rename files based on Serial Number & Description on the RMB menu.