But the Left Arm is also described in TGM as being rope-like is that correct?
Stretched taut (not stiff) through extensor action for both swinging (frozen rope) and hitting (beam)...
Yes, this mighty "Machine" sure has a lot of rope in it. Yoda calls it a "Noodle." The Swinger's left arm is all structure and is needed to act like a string with a wrecking ball at the end of it, like a clubhead, to be thrown at a golf ball. As part of its structure it is the Left Arm Flying Wedge.