I don't agree that it saves weight, its structurally inefficient to break the rear spar line, and this design actually hence introduces a structural weight penalty. Despite the root being much wider in ratio to the tip.
The trade-off is a higher AR, higher cruise and manoeuvre L/D.
In regard to the Sabre Dance, the problem being the tip stalling first (far aft of the CG) causing that deadly pitch up moment at low speeds. The lambda wing might alleviate this as the root still generates lift at the same longitudinal location where the tip has stalled - retaining the balance. Wow I didn't think of this.
So you can vary the area and and AR with a constant chord. Sweep a bit more without worrying. A very flexible planform if the wing has to come off and squeeze into a container with the fuse.