I'm guessing the author used the Japanese name Daishakuten instead of the Chinese name to make it easier for Japanese readers- it's also possible she didn't realize the Chinese name was different.
It makes sense that a Chinese merchant would be moved by a story of filial piety. One of the best known Confucian parables of filial piety is Lu Ji hiding oranges for his sick mother (though Lu Ji wasn't born at this point in the story), so this is probably a reference to that.