Tailsitter sdf, why elevator and rudder?

Iā€™m looking at the tailsitter example for SITL Gazebo. Why are there entries (link/joint/control channel) for an elevator and rudder? I thought the tailsitter would only have elevons.

If I comment out the elevator and rudder entries, it sure doesnā€™t fly stably in FW mode.

There are no visuals for the elevator or rudder, although there isnā€™t a visual for the elevons either. I actually tried adding a mesh for the elevons, and they appear to move appropriately.

Update: after further investigation. The ā€œrudderā€ isnā€™t actually driven by a control channel, so it doesnā€™t really move. It must be conceptually, just a fin. Perhaps it represents the combined aerodynamic action of those two inverted-V fins that it stands on when itā€™s on the ground.