So if your pages are already in xwiki/2.1 syntax this script is really not what you need since the main point of this script is to do syntax conversion. That means that itemDoc.content is enough to get the content of the page in syntax xwiki/2.1.
It’s not very clear to me what you want to do with it, as it might have an impact on how to export the content. For example, if your pages contains xwiki/2.1 content then you could simply use the XAR export which simply produce a zip file containing an XML for each page with the content in it.