IMSCC backup fails to include identifierref to files/docs from Topics

The resulting IMS CC imsmanifest.xml doesn't include identiferref for linked files

Full steps:
1. A Moodle 2.2.3 course with direct links to DOCX files in the course files area
2. Create a backup, choosing IMS CC option.
2. Download, unzip, and examine the imsmanifest.xml (would also be apparent on an import) =

Expected: Files directly linked to from Moodle Topics are properly referenced as items in the imsmanifest

Actual: imsmanifest creates items with identifiers, but does not include identifierref to these files, resulting in no links. (The files do exist in the appropriate folder.)