I've said a number of times that a bus wouldn't be capable of making guests believe they are flying either.
That's why I hope that bus or truck - this is your ground transport to Black Spire.
You get shuttled down to Batuu, just like you get shuttled up to the Halcyon - and will be shuttled back down to earth at the end of your stay.
All they need to accommodate this is a different video in the shuttle room.
Then, once you're on Batuu, you board this transport vehicle to the Black Spire outpost. This way it can be a bumpy, jostling ride like a bus or truck gives, and not break any illusion.
If I'm wrong, I seriously doubt how they could pull this illusion off.