dumpRdf uses SqlEntityIdPager to fetch IDs by namespace linked to the entity type, and then does this:
$position = (int)$row->page_id; $entityIds[] = $this->entityIdParser->parse( $row->page_title );
This of course can not work for MediaInfo type entities since the title is not the ID in this case. I think we need a more advanced procedure there, since now page with same title can have more than one slot, and depending on the requested entity type(s) one or more of these slots may be entity IDs we're looking for.