Yes. The Flex Feeder piece (#14 below) should be utilized for every install, even those going directly vertical. While the feeder piece is designed to facilitate the Flex Pipe through the B-vent, it is also used to prevent any foreign matter (e.g. rust, dust, etc.) from entering into the flex vent.
A class of vent used for natural draft appliances (i.e. tank type water heaters). Not allowed for tankless water heaters with fan assisted combustion (all Noritz models).