These unnecessary lines of assigning a variable to itself is for completeness only.
With its comment I find it clearer that leaving them out completely. A matter of choice, of course

About xmlPartsPostponed ... the meaning was to have it as a part of the summary, see line 506:

echo "${xmlFilesPostponed} documents were not tested as they still have no XSD"

This should be:
xmlDocsPostponed=$xmlFilesPostponed+$xmlPartsPostponed
echo "${xmlDocsPostponed} documents were not tested as they still have no XSD"