[tevake]

The boat exceeding the true speed, has to do with apparent wind speed on the sails.

Sailing close to or across the wind you can add the boats speed to the true wind speed to determine what wind the sails are experiencing.
Going straight downwind the boats speed is subtracted from the true wind speed, so no way to get extra power to the sails

Looking closely at the sails on the foil cats the sails are sheeted in close to the centerline of the boat on most points of sail because as the boat accelerates the apparent wind direction moves more forward relitive to the boats heading, further enhancing the apparent wind speed.

Cheers Richard