I remember secret ending in "Once in a Lifetime". Well... This world is just another server from Eternum. And MC from Eternum played as MC from OIAL, but he didn't know it until he left the game. So, your words may be true. But I wanna think that both games (Eternum & OIAL) are not just random servers from "Eternum". I prefer to think that both games exist in the same world. Otherwise we wouldn't have seen mentions of Stabby Mike in the Eternum.
What secret ending? I messed up the romance story line of the teach and Judie, so maybe I didn't get the perfect ending. I was being too nice and the game assumed I didn't want to date them. By the time I saw I was locked out, it was too late. And I only had one save file.
If the MC of OIAL is the same as Eternum's, I can buy that secret ending idea that both games are just servers in the same giant MMO. But I still think OIAL happened. The book didn't help the cult take over. And the cult is reffed (referenced) in the game, Eternum (with a newpaper and some dialogue). I think Eternum is just another cult's way of taking over since witchcraft and cloak and dagger stuff didnt' work.
President Stabb is I think still president, but I only here about him when the MC is at school or around town. But I wouldn't be surprised if he is play Eternum. In this game Chang and Chop-Chop seem to be the "Stabby Mike" character. So i'm doubting Stabby shows up.
I think both games exists too. But I think OIAL ends where Eternum begins and Eternum is a lingering problem from the time in OIAL. Something the MC didn't notice that was allowed to thrive.