I don't know if this theory has been proposed before. Previously, I had heard a hypothesis that Gallant Island may be the same as Huang Yaoshi's Peach Blossom Island, but no proof was provided. My current hypothesis is that the Ode to Gallantry kung fu may be a spin-off of the various arts of Xiaoyao Sect. I'll give you my reasons.
The Ode to Gallantry martial arts consisted of drawings on cave walls along with a poem. The nature of Ode to Gallantry is such that the more you want to learn it, the more you are unable to learn it. That is why in the end the only person to master this art turned out to be an illiterate person who had no intention of mastering it. All of these attributes are similar to Xiaoyao Sect's martial arts. Xiaoyao Sect also had drawings on the wall that were super hard to learn. The only slight difference with Xiaoyao Pai is that people could experience fire deviation easily, whereas with Ode to Gallantry people just don't get any/much benefits. Wuyazi was known (to readers) for his excellence in the traditional arts, and the way Ode to Gallantry is carved out resembles that. Furthermore, the poem that accompanies the drawings is there to confuse the practioner, making the art very difficult to learn. This is very similar to the chess game that Wuyazi designed, in which Su Xinghe invited many people to try out, and which no one who wanted to solve it could. We know that Murong Fu and possibly Duan Yanqing would have committed suicide on the spot due to fire deviation if others did not interfere. Only Xuzhu was able to solve the chess game because he did NOT want to solve it. He was trying it out of good intentions.
Hypothesis: the mysterious creator of Ode to Gallantry is Xuzhu. He wanted to pass on the martial arts of Xiaoyao Sect, but only wanted a person like him to succeed. That's why he blended the Xiaoyao Pai martial arts into one called Ode to Gallantry, and made the new art impossible to learn for those who wanted to learn it, but easy to learn for someone simple and innocent like the young monk Xuzhu.
Discuss!