A little bit similar but the major difference is that gravity is part of the equilibrium in the kiter's case and hence the kite can get overpowered. That single red arrow through the big hooked fin in the sailrocket diagram does most of the work, and as long as the super high strength material doesn't fail it will hang in there when a gravity balanced craft gives up.
The kiter diagram shows that the force, shown by the red arrow, which is equal and opposite to the aerodynamic lift, is the sum of two forces in the kiters case - gravity and hydrodynamic lift.
For sailrocket the majority of the hydrodynamic force is generated by that one hooked foil to balance the aerodynamic force. One foil in the water one in the air, (with a few other control foils that do relatively little work). It's a concept that has been around for a long time, just nobody thought it was feasible or was brave enough to take it on until now.