I see there are a bunch of non official awing pilots: tycho, hera, sabine, etc. Are their points considered valid for casual games? Was there a poll on them or something?

as far as I know, Sandrem just sometimes adds stuff that seems fun to FlyCasual.

In first edition there was a custom card league that did some stuff like this, I think there have been some attempts to revive it but they've had little success.

In 1st edition Fly Casual, they were there as an option that you had to enable from the main menu. I'd prefer it goes back to that switch (even though I like playing with these pilots a lot). As far as how correct their points are, who knows? I wouldn't play them against other players unless you know they're cool with it ahead of time, maybe even talk to each other about the points on them if they don't feel right.