Another question about AI content.

How can non-Google entities identify AI-generated content? I purchased some articles from someone on Fiverr, and am wondering if it's AI. I purchased them before I knew as much about AI content as I do now (which is still not very much).

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Also, I read people talking about being punished by Google for using AI content. Is this "punishment" for an entire page, or maybe just the post where they suspect the content is AI generated?