I think you'd be right about BuzzFeed if this happened ~a year ago. Now, BuzzFeed has so much content, and they push it so hard on visitors, that I would be surprised if they didn't actually score pretty highly on this metric (although I was a bit unclear on if this was referring to URL level or domain level time on site). Also, so much of BuzzFeed's content are long lists with large images or gifs that people stare at that they aren't going to be hit as hard as UpWorthy (who pioneered the "You Won't Believe..." headline. Finally, BuzzFeed has actually gotten enough traction to now be able to hire real journalists to create actual content.