The lug sail is cut very flat. It get’s its shape from loosening the lines. When tacking, the sail has no immediate drive. So, the instructions for the jib were to add a little shape so it accelerates faster.
The lug sail will eventually pick up speed, but I like a dinghy type sail that responds quickly then flattens out with speed using sail controls. As an example, the sail outhaul was very difficult to adjust while underway, but a multiple purchase will fix that.
Ants