It is my position that a machine cannot reliably determine whether a string of characters that would look identical whether produced by machine or human was produced by either. While you could very well be correct, your method for making such determination is—in my view—severely flawed.
Edit: I generally dislike LLMs and other generative AI, just as I dislike the “AI detectors” that often use them in an attempt to determine whether any given text or image was produced by such. I personally know someone that would score high from having developed habit of writing in clear, generic style for work over many years.