Here is another electric hydrofoil being developed. http://www.electricvehiclesresearch....foil-powerboat
This one uses surface-piercing foils. It also correctly notes the higher speed potential for the surface-piercing arrangement. As with a planing hull, the surface-piercing foils will reduce wetted surface area as the speed increases. A fully submerged foil does not have that ability. The tradeoff is seakeeping, which is going to be worse for surface-piercing.
Fixed surface-piercing foils are known in particular to suddenly lose lift (resulting in a crash into the water) when running with a following sea. This is due to the foil encountering downward water velocity on the backside of a wave, resulting in reduced angle of attack and lift. They will probably have to learn about that the hard way.