english: It's because of the knowledge we have now, we can make sure the Earth is round, so they are just stating what has been proven, and if the Earth is one day proven flat, then that is what they will say.
non_english: これで、ナイトさんを、混乱させる！ナイトさんのテスト、✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✗✗✗✗✗✗✗✗✗✗✗✗✗✗✗✗✗✗✗