Because it isn't full articles -- just updates as they happen coming straight from the newsroom, more like tweets. It's not to say that people can't plagiarize, but it wouldn't be as easy or make as much sense as just copy and pasting an article.

There's not much in the post so I'm gonna guess it's a form of content fingerprinting like we see with YouTube's Content ID, plus whatever is used in plagiarism-detection software used in schools and universities.