He did nothing in the first three rounds. Even Conor wouldn't have gassed with that pace. Juiced Jones' cardio was amazing, yes. Clean Jones... we've not seen any aggression and volume to judge. Also clean Jones shoots a lot less. People say he was trying to beat Santos in his own realm, but after the Reyes fight I'm pretty sure he doubts his cardio.
His chin is iron, yes. That's barely any news. Jones has eaten some hard punches from knockout artists without a care in the world.
Yet there is one thing - when a fighter is dominant and doesn't get hit a lot, you don't talk about his chin. We now can see how great Jones' chin really is, because he gets hit a lot more.