Thanks for asking! In the 1st edition of the game we really recommended it being a twist. These days my opinion has changed, and I think it works better if players understand that it is coming and can accept that and buy into it. Ultimately, its up to you and what you think your group will respond best to.
In my own experience, having it be a twist is a great moment, but it sometimes leads to players who want to spend all their time trying to open the door or find a loophole to get home instead of embracing the game's story.