In my opinion, there are multiple words AI uses that a normal human being won't use while writing. As mentioned above, lack of emotions, sentence lengths etc. But, to be honest, after fine tuning gpt blog posts, let's say 150-200 words, I was managed to make it look and feel like it was written by a real person. However, after submitting it to zerogpt for example, it said it was AI generated. Went through the whole blog post again, and it was something I would write by myself, but still, it was flagged as 100% AI written.
This got me thinking.. I pulled a few posts my writers wrote back in 2010, 2011, 2012 and even tho they were working in the office, they were flagged as AI generated content and trust me, these guys / girls were not smart enough to use anything to generate content. The tasks were so personalized, and it would take ages to train an AI model to do what I needed lol
Conclusion, don't rely on what AI content detectors say, they make mistakes. Even for verses from the Bible, it can say 100% AI generated or content with mixed signals with some parts generated by AI/GPT.
ps. in my experience, ai written content is not a bad thing for your website, but it requires lots of work and patience to get the results that would fit in todays f*cked up SE world..