AI allowed or not allowed by Google in Google, it is still not crystal clear. Nonetheless, Google uses (or will use) AI to detect AI, in other words Google uses (or will use) AI to detect what "quality" a content is and AI is never (as yet) perfect, so the detection of AI by Google's AI detection also is (or will be) flawed in a way that non-AI content could be detected as AI content and AI content could be detected as non-AI content.
The best solution is for Google to hire 1 billion human beings in order to manually detect AI content, until the time comes when AI detection is perfect enough to detect AI content.