Nobody has taken down Usman like that without care. Maybe he's trying to save face, whatever. Also Khamzat fractured his arm in the first, still managed to take him down and win.
"Usman with an extra 2 rounds" "Usman with a full training camp", well then imagine Khamzat with a full training camp for Usman and not fracturing his arm.
In fact Usman showed himself getting a last minute Masvidal he couldn't do much with, even though he had a full camp. Then with a rematch he KO'd him fairly quickly. I'm sure you could argue Khamzat would do even better as well, because it's the same scenario flipped.