User blog comment:The Milkman/No Love For Leviathan?/@comment-4953843-20120916071319/@comment-24174486-20120916132955

Your squadmates get killed off in the original endings as well.

Since half of the squad in the base ME3 can either have died in ME2 or be killed in ME3, the game ensures that you have at least someone with expertise in Tech (EDI), Biotics (Liara), and Combat (Vega). That's likely part of the reason why he pops up—because he can't possibly be dead during the events of Leviathan and the scene wouldn't quite work with EDI or Liara.