Why does Zhang Sanfeng think that the Jiuyang forces of Shaolin, Wudang and Emei are one?

Zhang Sanfeng thinks that the merits of Jiuyang of Shaolin, Wudang and Emei are combined because the memories of Jiuyang's merits of the three factions are incomplete. The merit of Shaolin Jiuyang was handed down by Shaolin colorless Zen master, and Guo Xiang later founded Emei School, and the merit of Emei Jiuyang was handed down. Zhang Junbao later changed his name to Zhang Sanfeng, founded Wu Tangzong, and handed down the merits of Wudang Jiuyang. The merits of Jiuyang of the three schools are all derived from Jiuyang's merits, but the effect is much worse than Jiuyang's merits. Therefore, he wants to find out the merits and demerits of these three schools, and then merge them to restore the complete version of Jiuyang Classic.