1. Game was advertised as something that would always stay wholesome since the beginning so it feels like betrayal this late in development and 2. the fact that there is a possibility of hard NTR happening changes who Hana (and Yuma, assuming it would be with him) are as characters. Currently we can always be certain that Hana loves Tatsuki and their marriage will endure everything, the netorase is just play for them. However, if there is suddenly an ending where Hana actually gets stolen it retroactively makes it so that it was always just a matter of the right event to happen to make her leave Tatsuki, which feels like character assassination.