I don't see any advantage either because propelling a boat with a displacement hull is all about speed. You can propel a displacement hull up to the hull speed where the length of the bow wave equals the LWL pretty efficiently with sails. The amount of power it takes to exceed hull speed increases exponentially. Most modern racing yachts can sail up to 2x hull speed and 3x wind speed on a reach with the right rig and a big roach main. Cruising yachts are a little slower but still most can pretty easily sail at 1.2x hull speed.
The sails on our yacht develop the equivalent of many hundreds of propulsion horsepower because they work like an airplane wing and develop lift. I do not see being able to do that by harnessing wave power, and especially being able to do it on points of sail. As you say, Norm, sails have been used to propel boats since at least 300AD as recorded in the ancient Viking archives stored in Nuuk, Greenland. And to this day, the record for a circumnavigation of the planet by a boat is held by a sailing yacht, and it beat the fastest mechanically propelled boat by about 15 days.