I am not confident from the pictures that this is the same thing but Prone Paddle boards have had a 2 in 1 steering for a long time. They use the batten steering etc but it has worked for them for ages.
The extremely rough diagram below shows how it works.
The fixed fin at the front holds the board in a line and directional, the rear section of the fin is free and controlled by the batten or steering system which steers the board. This would stop the board under rudder and the board still sliding sideways thing you get in the surf etc.
To me it makes a whole lot of sense.
