Alright, that pretty much confirms my suspicions. The other thing I'm wondering is, did the Allagans work on the other beast tribes as well? Like, say, the Vanu Vanu, or maybe even the Amalj'aa?

I dunno, I'm likely overthinking all of this because we never really got a good idea of where these two in particular came from, other than "They were always there". At least with the Sahagin/Kobolds we're told that they came from the sea/underground, respectively, at least as far as I recall.