Unfortunately not the best headline. No, quantum supremacy has not been proven, exactly. What this is is another kind of candidate problem, but one that's universal, in the sense that a classical algorithm for it could be used to solve all other BQP problems (so BQP=P). That would include Shor's algorithm, and would make Q-day figuratively yesterday, so let's hope this is an actual example.

Weirdly enough, they kind of skip that detail in the body of the article. Maybe they're planning to do one of their deep dives on it. Still, this is big news.