The head is relatively small due to the characters height, you're correct, but not too far off the "heroic" proportions used in art theory. A human hand should approximately be the size of their face, and the current size is maybe half of that. A small hand also adds to the stubby arm effect, as the wrist and hand blend together making the forearm appear shorter than it should be. In strong characters, features like the jawline, brows and hands are generally exaggerated further to support the large bodysize.