Something just being referred to, internally, as a third show that wouldn't make the website. Sounds like a scare zone show on steroids where they're treating it like a show, but it's not in a specific venue/area with some kind of gated area to get into.
Or maybe a scare zone with a big dance number or something where they are hiring professional performers (past Bill & Ted dancers) and choreographers, but it's not going to be called out as a show on the official site or map.
I would LOVE for there to be an unannounced Ghostbusters mini-show like Blues Brothers where every 90min or so, and Ecto-1 drives out, blasting the ghostbusters theme song, and then there are a few actors who get out and do some kind of little mini show, get it the car, and drive away. I've been quietly hoping for that since speculation said no GB scarezone.