So what? There's plenty of dubious blogs claiming all manner of things. The actual accomplishment isn't noteworthy (they wrote a scraper). If it were encryption-breaking, it would indeed be noteworthy, and thus worthy of fact-checking or at least waiting for Signal's rebuttal of "lolwut, no, that's nonsense".

"Accuracy" is moot here: BBC's headline is misinformation.

No, it didn't. It specifically stated that access to the Android keystore was needed to get at the stored Signal data.

There's a blog post claiming the Earth is flat. Would the BBC publish an article on it outside of satire?