They're humans - and I have my reasons for classifying them as such. The "chosen" lightbearers are all humans in some form or another. You've got humans themselves, Exos which are humans in a metal shell and Awoken who are humans that were destroyed and reassembled in another pocket universe. The sole exception seems to be Felwinter, and even then, he was an AI that was essentially made by humans, to emulate a human. So, what are they? Humans. Why are they different? Literally space magic.