I believe that small wing placed on the right sponson was an attempt to keep the rights sponson from lifting in the turns. When the hull (& sponson) is turned left, the airstream will flow over the right sponson sideways. The shape of the sponson causes it to act like an airfoil, causing lift on the right front corner of the boat (while in high speed left turns (on a full sized unlimited)). There are videos on-line of the Bud rolling and flipping to the left while exiting turn 4, in several races back then.
The issue was finally solved by replacing this little wing (shown in your pic) with a vertical clear plastic sheet/air dam on the inside face of the right sponson, extending several inches up above the level of the deck. This clear sheet acts as a "spoiler". It cuts the lift when the right sponson is canted into the airstream at an angle to the travel direction of the boat. It interrupts and deflects the (crosswise) flow of air over the top of the sponson, cutting its lift, when in the turns.