Note that Asura's a name we've already claimed for a race of outsiders—a race of lawful evil outsiders based heavily on Indian myth. We've only statted up one Asura so far (in Pathfinder #9), but another one's on the way at some point in Council of Thieves.
Both "Agathion" and "Azata" are based on real world mythos, though. Agathion is a Greek animal spirit, so it seemed logical to make the NG animal-headed outsider race agathions (and having the 1st edition agathion itself be a NG creature from the outer planes is a nice bonus there). The azata is a bit more obscure; the original spelling is in fact "Yazata" and they're from a Zoroastrian concept (check out the Yazata entry in wikipedia for more info).
So while both "guardinal" and "eladrin" are merely made-up words, the names for our equivalents in the PRPG are based on real-world myth and sources. This is a case, I think, where not being able to use the names that WotC claimed as their IP ended up spurring us to come up with even better names, personally!
EDIT: And yes, the Bestiary itself is world neutral. That said, it DOES work perfectly in Golarion, and while the angels in the Bestairy are listed as being ANY good alignment, that still allows Golarion to have mostly NG angels. Although I suspect that as time goes on, you'll eventually see some angels branching into LG or CG in Golarion. They're certainly one of the more wishy-washy when it comes to alignment among the outsider races.