The ij.driver property is not useful any more and can be removed from the documentation. According to Rick Hillegas, "The purpose of the ij.driver property is to tell ij to manually load a driver class via Class.forName().newInstance(). That's the ancient way of loading drivers. The modern way is to rely on driver autoloading."
The Driver command may still be useful for reloading the driver after the Derby engine has been shut down and the driver deregistered, so that can be kept.