The three blade approach also offers better outcomes for repair costs (and animal strikes). High-blade, high-solidity designs are more likely to break in extreme weather (even a stopped windmill takes a lot of strain at 70% solidity) and repair is usually necessary after failure of a single blade.

Between that and your points, my impression is that many-blade designs aren't useful beyond small scale generation, which is exactly where they're still in use. There are an awful lot of three-blade advantages that went completely neglected in this piece.