It's a general feeling more than a precise diagnosis, and I guess it could also be a human that has internalised LLM style, or a human-written draft that was reworded by an LLM. But it just really feels like LLM writing.
As I said, the actual remark I made is independent on whether this article was written by an LLM or not.
It's still pretty obvious to me that it was, but I'm not sure what kind of "proof" you are looking for, you know as well as I do that it can't be proven one way or the other, so who cares?