It's more important in the light to moderate wind when you want to ease the outhaul and have a nice shape in the lower portions of the mainsail. Your sailmaker should, adjust the sail to really take advantage of this option while allowing you to still flatten the sail in higher wind speeds without having to use a flattening reef.

It also makes the sail easier to pull off and install.

I assume you won't be using full battens and a lazy jack or Dutchman system?