Well yeah, and I'm sure Justino walks around bigger still. I mean, I get that some great fighters are willing to move up a weight class to fight. Is Rousey really a great fighter? Maybe a pioneer of sorts, but great? She was exposed by Holm and the shine is off. She built her brand well enough to make good money. If she fights Justino it will probably be one last big payday before she hangs it up. Crazy to do that if she isn't quite done yet because she knows damn well it will be a difficult fight for her that she will probably lose unless she can quickly grab an armbar. Another big loss and the shine is off even more. Of course that can still happen with Nunes, but at least Nunes is in her weight class.
I'm sympathetic to Cyborg because she is great herself but doesn't seem to have the quality opponents to really define her. I'm not sure calling out a big name in a lower weight class really changes that much, though she would get paid better.
I know you're a student of the game. While guys do move up, how often does someone in a higher weight class call out someone in a lower one? I don't know the answer. Maybe it happens a lot.