We experienced exactly the same: The USOB_SM entries are missing in the download file as well as the modifier date stamp, so we decided to desert it.
- If there is no need nor intention for customers to maintain your entries further (so no need for SU25 to transfer it either), then deliver them as SU24 workbench transport entries. The customer can import them via the normal transport route or you send them with the application. That works best.
Otherwise you must manipulate the file to add the expected USOB_SM entries for other object types (RF and HT).
Cheers,
Julius