Yeah, it's sad that most of these other aliens are just thow-aways mentioned once and then never again.
The Arcturians got lucky, being mentioned again in the new novel trilogy.
But not fully described so we have no clue about them besides that they aren't forgotten.
I would love to see you put up any new info should you get the chance to play through the game. From the gameplay footage I've seen, it looks quite fun. I like the charm these vintage shooters have, being simplistic and arcade with the old graphics.
Even the old AvP games added new creatures in them while the new one just felt rushed. (Still is really fun and I have replayed it so many times that I lost count)