It's the overall structure of the article, the cadence itself, those short punchy sentences, negation. If you want some better evidence, Pangram flags 1/3 of this article as AI generated, but that's because they'd rather have a false negative than a false positive.
If you want another funny evidence piece, see https://lab-stack.com/blog/dgx-spark-memory-hard-wall/ - a random article I found by direct phrase search. It has a similar structure and "My initial theory was simple" word for word.
Edit- upon rereading I think this is probably human written, but definitely has the LLM / LinkedIn style. In any event, it’s probably as close to be experiment I mention above as I’ve seen.
I sometimes ask an LLM to explain something to a certain kind of audience. Usually I need to ask it to keep things briefer and which things to really focus on. I typically do 2-3 iterations and then manual editing to make it feel like 'me'. This would be for a 2-3 sentence kind of thing.
Not a native English speaker. I used to think I was pretty good, but I get way less misunderstood this way.
(I didn't use an LLM for this message.)