That's a new epithet for Luke. But there are ways in which he doesn't even look like Luke. At all. It's not just the age (as with Professor McGonagall, he's really not sure whether he thinks Lucius looks actually too old or just unusually careworn). There's something about the eyes. Not a softening--no, if anything, there's more of a sense of accustomed steel to them. A feeling of acknowledgment, perhaps, that some other people might, just possibly, be real. And, well, looking at a Malfoy it's impossible not to see the pride, but the inescapable impression of a strutting contained flutter of peacock feathers is missing. And, given that the man is flustered, that's outstandingly unusual.
"Unquestionably," he says for his own assurance, everything else but his self seeming highly questionable at the moment. Professor McGonagall had said something about people who thought they knew each other having come from different probability streams, but then again, he always had thought that if Luke ever grew up he could become someone impressive. Eyeing him critically, therefore, he asks, with more bluntness than any overtly acknowledged sense of irony, "What happened to you?"