In the canonical, novel depiction of the Second Mt. Hua Sword Tournament, North Beggar Hung 7 Gung and Gwok Jing both used Hong Lung 18 Palms during their duel. In TVB's 1982 LOCH adaptation, however, Hung 7 Gung specifically ruled out Hong Lung 18 Palms because he felt it'd be rather pointless for he and Gwok Jing to duel using the same skill. Therefore, they elected to go for a weapons duel.
Though non-canonical to Jin Yong's original novel, I found Hung 7 Gung's reasoning in the adaptation sound. Why not use the Dog Beating Stick Technique to duel Gwok Jing?