Putting canonical things in a JAP version while leaving another region in the dark about it can cause story confusion, since they are missing out on stuff.
Not all people turn to youtube.
This may not even be a canon fight though. I sincerely doubt it is. No Heart might simply be proving that Xemnas CAN wield a Keyblade. It's not a coincidence that Nomura hinted in an interview that "Xemnas may have been able to wield the Keyblade but chose not to" and now this boss shows up.
And that didn't stop SE from putting in the "Room of Sleep" and "Lingering Sentiment" cutscenes for KH2FM even though the game was never officially released in America.