Doesn't sound like reality to me. The article looks very much AI-generated. Nothing to do with not being an English native speaker.

hm, I don't have any other ways to prove it. The thing is - I thought this is something LLM can't write about.

Just imagine a prompt: "Hey Claude, go ahead and come up with idea why GnuCash stores numbers as fractions and come up with an article for HN". I actually tried it and god damn thing came up with something very similar :D