Will I would tend to agree. Had the actuator pushed the spoiler up into the airflow (travelling in the designed direction) but above the designed deployment structural speed, there would likely be convex deformation on the upper surface above the actuator attach point, and failure signatures on the hinge attach points.
There are not too many circumstances that would have a wing facing aft into airflow strong enough to do that. That is not to discount the possibility of this having happened as a result of the wing impacting the water trailing edge first.