Sadly, this didn't seem to track for LLMs. Even OpenAI gave up on trying to detect its own outputs.
> As of July 20, 2023, the AI classifier is no longer available due to its low rate of accuracy. We are working to incorporate feedback and are currently researching more effective provenance techniques for text, and have made a commitment to develop and deploy mechanisms that enable users to understand if audio or visual content is AI-generated.
You're not classifying just text, you're classifying entire web pages. If it's easy to tell for a human that it's SEO spam, it's easy for a classifier.
> As of July 20, 2023, the AI classifier is no longer available due to its low rate of accuracy. We are working to incorporate feedback and are currently researching more effective provenance techniques for text, and have made a commitment to develop and deploy mechanisms that enable users to understand if audio or visual content is AI-generated.