I think you may be right. Gossamer Gear is now making some smaller sizes (torso length 12 to 16 inches) but their older packs like the G4 have only two sizes and 16 inch torso length was at the bottom end of their smallest size.

My 12 year old daughter has a 15 inch torso and my 14 year old is the same size. Of course on top of that I need to get some packs for my 9 year old and my 6 year old. For them I'm thinking a belt-less pack would work best.