All of the IKA kite race boards carry too much fin and the center of pressure is not perfectly dialed in for half wind. A kite board with much less fin area, altered stance, and a kite that is made for half wind efficiency will definitely be faster.
It also depends a lot on the conditions in super gusty conditions the wind surfers have a much easier time holding down the power compared to kiters.
The figure 8 slalom during the RRD races in Denmark were dominated by windsurfers due to the conditions. The four slalom races on Saturday were much more even and non of the kiters had specialized slalom gear and still managed to compete with the top wind surfers. Of course I was competing the bottom quarter of the field due to my bad gybes and non ideal kite