AI Plagiarism Checker

This app claimed that passages I wrote without AI assistance, not even basic spell check assistance, were written by AI. I tested it multiple times. The rationale given was often “reliance on common tropes,” which would make sense if the novel was not intentionally based on tropes common to many werewolf novels. Are they trying to promote use of the humanizer? Am I actually only 5% human? Maybe I need to ask the Moon Goddess.