I still can not remember seeing similar things to this done on other square top mainsails, and I really think I would notice?
The way you describe it, it sounds like a fickly thing to get right. Wonder what happens with the sailcloth around the reinforcement, as it would probably stretch more and create point loads in the cloth.
Hmm, if done like that, perhaps even a crosscut dacron sail can be buildt to give reasonable performance..