Yu Yevon wasn't really the final boss. They just had to finish the story by you beating him. And you don't want to go through fighting all your aeons again do you? Braska's final Aeon was the real final boss. And he is challenging if you don't get damage break and 9,999+ HP. Which you will have to do sidequests for. Hence, they're more like the cheats for the game like the author originally applied.

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