Is MailStream Plus able to upload only an electronic Postage Statement to the USPS rather than uploading the Mail.dat files?

Product affected: MailStream Plus™, all versions, all platforms
No, there is no option available for uploading just a Postage Statement to the USPS.

The Mail.dat files can be uploaded to the USPS PostalOne! site, and from the information in them the USPS can generate Postage Statements (as well as other reports.)
UPDATED:  May 15, 2019