The story is nice but some details ruin it IMO.. How would a salesman know how to command an army ?
Also, the success of an army depends on a huge number of factors, not only dryness of hands.. Military strategy seems more important than hands
All that to make a more general point: if you have the wrong expectations for the way something is, you're going to suffer because of those expectations. The silk-washing family was frustrated because they believed the balm could only be used in one way which kept them very poor and worn out. Huizi suffered because he was gifted seeds for some very large gourds, but expected to use them like normal-sized gourds, and eventually destroyed the gift after expending much time and effort on them.
OTOH: “The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.” -- George Bernard Shaw
Can't wield weapons without hands.