How do we know this isn’t AI?
 replies(3): 
A subjective answer is, if you have been there and know this to be real from personal experience.
A more general answer would be, as long as we humans sufficiently interact with reality, we will have a respository of life experience to benchmark against.
Once we cease to do that, and are the product of a life in front of the screen, then we won’t know anymore.
Edit: This place is relatively close to where I live.
We only know now because generated things still have artifacts. That is slowly changing. If the article was written by an AI right now absolutely cannot be fully known.