Yes, you can! The rules clearly state that a torso can only twist for 120°. Not a degree more! There is no rule how fast that twist is, so implementing different turning speeds is possible without violating the rules. If you want to stay true to the rules, something microsoft obviously didn't inted to do, but PGI wants to, you implement a stop of your torso at that very angle.
It gives every single mech a weak spot, no one can ever evade. It is balancing in itself, because it makes fast mechs with good turning speeds (probably light mechs mostly) viable against slow turning behemoths. If they had to outrun turning and endless torso twist, they would stand no chance.
This is not the arcade shooter MW4 has been. This is a totaly new and unkown beast.