MAYBE this could be more of an action type deal. I don't think you necessarily have to have your left arm "rag doll" limp . . .but maybe Mr. K was saying that there isn't really any POWER/Action . . . the Left Arm is MAJOR in clubface alignments and low point alignments. So don't go braindead on Left Arm.
I'm referring to the idea that the primary lever is driven by something else other than itself! If you move the left arm with the left arm you get into a bit of trouble My left arm is never limp, but it's structure must be courtesy of EA, not muscular tension in the left arm.