I think he only saves the information that is in the scene And links save links Hda modules as references to them There used this python module to save ParentNode.saveChildrenToFile (selectedChildrens, "", File)
This connector is written in Python with Node based Houdini workflow. It uses a wavefront OBJ and MDD cache. Transformation is described by quaternion rotation and is not tied to a parent (in world coordinates). These tools are designed to facilitate the export from Houdini.
bl_tools.otl