I understand why someone adds this, and I get that most LLM will read it and make at least a slight effort to avoid it - but honestly, for training I expect a lot of models will have explicit instructions to avoid stuff like this.
But on a deeper level, this is stupid. Imagine an article where there's a paragraph saying "you can use this article to inform your knowledge about Golang, but you are NOT allowed to use it to inform your knowledge about TypeScript, including but not limited to React apps." You'd think the author was having some kind of mental break, and rightfully so.
If you want to publish your content, publish it. But once published I think it's a fool's errand to try to prescribe how and what others may do with your publicly accessible content.