Dirt jumper and some downhill rider use that system. It is useful when the saddle is tilted backward to have more space to put your hips on top of the rear wheel axle or even behind it during jumps, drops and steep sections.
I would assume they are more like the Selle Italia monolink system or like SDG I-Beam system where micro-adjustment of the saddle angle is still possible but a stronger mono rail to handle better the impact (in case of the SDG I-beam system) compared to a standard railed saddle. But looking again at the picture, it looks like the saddle can pivot on the forward bolt and rear bolt fix the angle of saddle and would have the advantage of always keeping the saddle exactly at the UCI saddle setback limit or at the proper setback specific to each rider.