It doesn't help that the linked article never bothers to explain this either.
This article was written for a specific audience who follows this blog because they know the term. If you start spelling out fundamental acronyms it makes the content look more basic and general.
This always upsets the general audience who stumble upon the article (like this) but it wasn’t meant for a general audience. CTF is extremely well known and the people who would be interested in this topic would wonder what’s happening if it was spelled out. It would be so odd that it would probably attract accusations of ChatGPT writing.
Informal writing about technical topics is another story. There you can assume a lot more shared context, as you are only writing for a specific subculture within the field. It doesn't matter much if other people in the field fail to understand you.
But that is about you right? Its a little entitled to expect every piece of content on the internet to have a 101 explanation attached. If they were specificly aiming to have the blog post appear on HN that would be one thing, but they (presumably) weren't.