I believe that the section on your main login page pertaining to additional documents has some fine print above it stating to the effect that:
"Additional supporting documents can be uploaded for use when completing applications."
It seems as if it is just an online "holding tank" for your convenience to store documents to expedite the filling out of future applications. This is also why I am skeptical of the ability to upload more documents to your specific job application after it has been submitted merely by putting the documents on the "main login page". To me it seems as if that is just a user tool, and doesn't mean these documents are published anywhere.