AI-generated content has really dropped the floor on how cheap it is to produce niche blogspam, and they're saying: "Hey if you're pushing out 1000s of articles a day on a topic and we look at it and it's insane gibberish, we're just going to assume it's no good on principle and ban you."
Nobody is getting banned for the "Gray-AI" of assisted writing, where you get help with an outline or use Grammarly Pro to rewrite your sentences into coherence.