It is used to stabilize aiming.
More like stabilising sustained accurate fire. Note that he has the LMG version of the 95.
The bulk makes me think it’s unpowered and relying on mechanical and hydraulic parts to help control recoil rather than powered servos, which could be made a lot more compact.
The benefits to an unpowered frame is that it should be lighter since it won’t need a power pack, and would also be much cheaper and have a much smaller logistic footprint.
I am hoping they will combine the unpowered leg frames with these to give a complete set at some point. Although the fact that the two parts are designed for different applications may mean it is not so simple or worthwhile to do so.