Luke's reaction made Obi-Wan falter slightly again. "Yes, and I know someone named Luke," he supplied. "Though he's nowhere near your age. I'd ask where your Ben is - but if you are who I think, then I can probably hazard a guess what happened to him."

He's under no illusions how his life would end. It was rather disconcerting to meet someone who knew conclusively, though. And Luke had to know that he's dead, for he said 'meant' a lot to him. Past tense was always a clear indication of whether someone was still among the living.