My upper two battens have the same system, which I consider quite clever. Just don't lose the 'stuffer'. No problems with mine.
The ice boat also had full upper battens with adjustment by turn knobs working mini screw jacks trying to stretch the sail and shorten the battens.
And as I recall, the original America Cup Catamaran had a soft sail with full battens adjustable from deck level through a system or cords running up the luff of the sail and then out along the pockets.