From longtime user Perceptive Coot, an updated version of Spec Map they made!
If I was going to have an external group be your "Headliner" External IP for a prototype park that would be your first time, I would argue you go all out to give them some kind of a dark ride.
Plus, it isn't uncommon for LEGOland to have dark rides. The Ninjago attractions plus LEGOLand Factory come to mind.
Another point in defense for a SpongeBob Dark Ride comes down to that of the showbuilding size for what seems to be it is likely the largest showbuilding in the park at the start. On-par with the Hotels; it's a beefy boi that I doubt would be just for a M&G or a flat.