It's absolutely LLM prose, though not all of it. Maybe the author rewrote parts.
The thing that concerns me is that even at a site like HN, where a lot of people are very familiar with LLMs, it seems to be passing.
I hate to think this will become the norm but it's not the first HN linked post that's gotten a lot of earnest engagement despite being AI generated (or partly AI generated).
I'm very comfortable with AI generated code, if the humans involved are doing due diligence, but I really dislike the idea of LLM generated prose taking over more and more of the front page.
Of course it will be new normal. Even worse in few years you will be writing yourself AI-like prose cause of all of that AI written article and news that you read, will cause silently for you to adopt that style. In few more years barely anybody will be able to write coherent statements themselves without help of LLM :)