Maybe it's because no one has been more dominant of a grappler than him, if you take into account both gi and no gi titles. Maybe it's because no one his size has been as dominant in the absolute division of Abu Dhabi, or that he has two "Most Technical Grappler" awards. Maybe it's because even with the loss to Popovitch, he looked amazing leading up to that point, before losing the match (which could also be argued).
Is Roger unbeatable right now? It definitely looks like that, but Marcello only competes
at the tournaments that matter and i think people forget how dominant he is. By the way, I love Roger and think he's unbeatable right now. Marcello can't compete with his size (even though everyone was holding their breath when he almost choked Roger out).