GGG's face was visibly marked up early in the fight. Even the commentators mentioned it. By the end the early bruises had faded and his face didn't look marked up anymore, but he clearly had several red marks all over his face early in the fight. As far as why GGG looked fresher and less gassed than Canelo did after 12 rounds, that's obvious. GGG didn't come to fighht. GGG only fought hard and was landing in the last 4 rounds, whereas Canelo fought hard from the opening bell and was landing all 12 rounds. It's easier to not tire when you do nothing for 8 rounds and only start fighting in the last 4 rounds than if you fight hard all 12 rounds like Canelo did.