I believe step file names come from the step file itself. Creo/ProE just follows the file. You can open the step file in an editor like notepad and view the information there.
Sounds like you might be renaming the assembly (save a copy) and using rules to somewhat automate it. If not, it's worth a try to see if that can help you any. You also might look into step file viewers or utilities to see if one of them has the capability to rename the parts before they are imported but I suspect that will be hard to find.