Zuko had to admit curiosity to her first comment, but he tucked it away in his brain for now -- he would, indeed, ask Draco later. If he remembered.
"Oh..." Zuko said, shrugging. "I usually get up early. I was just kind of trained into it as a child." It wasn't that he liked it or disliked it; in fact, he didn't even really think on it. He just woke up when he did.