This basic idea has been made/reinvented in two forms: passive wrap-around frames like the Jansport you mention as well as the Coleman plastic frame; and active leveraging devices like the 'weight balancing' frame. To my knowledge, no one has mass produced any of active leveraging devices. They look good on paper if you don't look too closely, but the prototypes have failed to meet expectations. Notice the date on the patent application. The idea wasn't new then. It's just that it didn't work, so no one followed up. Wrap-around frames don't work that well either. The theory is that they place the pack weight over the hips, closer to the user's center of mass. Of course, that ignores the basic mechanics of leverage. All it really dies is enable the pack to sit up on its own. In the Coleman design it gives the plastic frame extra structural support that it needs.