That could be true. I just don't get how Halsey can say that stuff without being there though, doesn't make sence. She probably assumed he/she died. As for getting off Reach? No idea really.
I only have one theory. Just before the red Elite 'stabs' Noble 6, one Elite gets in the way. That Elite's Energy Sword was in the left hand and if I remember correctly, only the Arbiter uses a sword with his left hand. You don't actually see the Elite though, just the hand and the Energy Sword. For some odd reason; if it were the Arbiter, the Arbiter could've taken Noble 6 as a prisoner. That's one way to avoid the glassing