It is uncertain why Sadaie made such a difference, but one theory pointed out that Hyakunin Issu contained poems by Emperor Gotoba who had been sent into exile by Kamakura bakufu (Japanese feudal government headed by a shogun) due to his attempt of the Jokyu War, but none was found in Hyakunin Shuka which was published after Hyakunin Issu; therefore, Hyakunin Shuka was the revised version of Hyakunin Issue based on Sadaie's political consideration.
なぜこんな事をしたのかは定かではないが、承久の乱を計画し鎌倉幕府に流罪処分を受けていた最中の後鳥羽天皇の歌が、はじめに発表された「百人一首」にあり、後の「百人秀歌」にない事から、「百人秀歌」は定家の政治的配慮がこめられていた「百人一首」の修正版ではないかとの説がある。