It has several. The big ones are even sentence rhythm, predictable word choice, tidy punctuation like em dashes and curly quotes, and boilerplate openers that could fit any topic. Detectors read these patterns and score how machine-like the text feels.
That's why editing beats tricks. When you break the rhythm, swap the stock vocabulary, and add specific details, you remove the exact signals the scanners rely on, and the writing reads as human because it is.