When it comes to the results produced via Special:ExportRDF I have the feeling that the parameters recursive and backlinks are ignored as soon as "$smwgAllowRecursiveExport = true;" gets set.
I always seem to get the recursive export no matter if I check the option on Special:ExportRDF or not. The same applies to the GET parameters. Additionally GET parameter "xmlmime=rdf" does not seem to control the output generated, i.e. the output seems to be all the same.
I feel like a veggie when it comes to this so this is a report of my observation which may well be wrong.