One explantation for vertical battens for us in a jib: http://news.mesailing.com/msp/2012/02/vertical-battens.html

North Sails - http://www.ru.northsails.com/LinkClick.aspx?fileticket=cGjIEmU7GCs%3D&tabid=41705

Al, I think you meant that fully battened mains sometimes have the upper sails partially battened (more tradtional), but almost always have the lower ones fully batteneded. Ours have allways had fully battened for all of the battens; however, I know a number of people that think the upper two dont' have to be fully batteneded.