I'm pretty sure the aliens are "true" Xan. More than likely, the "Redeemed" side.
The Xan had no "redeemed" and "unredeemed" sidings. They were just "good" and "bad" Xan.
Like, they prolly called each other:
"Mystic Porn Stars"
and
"Flashy Super Queens"
or something stupid like that. The Unredeemed and Redeemed could only recently become "redeemed" and "unredeemed" because they only recetly could access their homes and take control of their people.
What you gotta think about is... where are the "good" Xan at, prior to Shadowlands? We know exactly where the "bad" were. There is never any mention of the "good" though, is there? Correct me if I am wrong. I know David was chosen but you never see these figures, do you?
What if the Aliens are the "true Xan" -- "good" side and David was their counter-act to the "bad" side that was leading humanity towards Rubi-Ka in order to get back to Eden?
Somebody sealed the source with the expectations that if anyone got there again, the Beast would kill them. They didn't count on outside influence -- nano tek, spirit tek, ect to aid us. In RP we use advanced weaponry, in reality we don't see it as such but our bullets and stuff are probably like enchanted now or some crap.