Doesn't a 4 blade prop lower your top end? If so, wouldn't that be an unbalanced comparison if top speed is a key factor in the total outcome?
From what I saw, they weren't comparing performance based on speeds as much as engine RPM. At the same RPM, the Sharrow prop gave more speed allowing the boat to plane at said lower RPM. If a boat planes at 25 mph, then that is where it planes whether it's at 5000 RPM or 3000 RPM. Obviously, there would be more fuel consumption at 5000 RPM so using speed as the key factor would only prove what speed is needed for that particular boat to get on plane and not the fuel savings/performance the Sharrow prop is proposing it gives.
It looks like the idea behind the prop is to give 4 blade low end performance while keeping the top end as well.