Can't convert directly from Confluence package to XAR package with xwiki/2.x syntax

If using the WikiStream application to convert a confluence.xml.zip file to a XWiki *.xar archive, the generated content has an empty <content /> tag.

To reproduce:

• install the WikiStream UI
• in WikiStream/WebHome pick "Confluence XML import stream (confluence+xml) for the Input Type and "XAR output stream (xwiki+xar/1.1)" for the Output Type (and add e.g. some of the test data from the xwiki-platform-wikistream-stream-confluencexml as Source file

I guess the problem is that in the content is written in the XAROutputWikiStream.beginWikiDocumentRevision
and expected to be read from the FilterEventParameters coming in there,
but in the ConfluenceInputWikiStream.readPageRevision where this method is called (via proxyFilter), the content is not stored to the documentRevisionParameters