I've noted before that because AI detectors produce false positives, it's unethical to use them to detect cheating.
Now there's a new study that shows it's even worse. Not only do AI detectors falsely flag human-written text as AI-written, the way in which they do it is biased.
This is
Stephen Wolfram’s article on how ChatGPT works was enlightening: https://writings.stephenwolfram.com/2023/02/what-is-chatgpt-doing-and-why-does-it-work/
Like you said, it’s just text prediction, using online content as the training ground.