My impression, taking game design and Japanese culture into consideration, is that Nintendo was ok with blocky pre-vis and rough outlines.
Think of the early art leaked for Mario Kart and how blocky it was, and how some areas don’t quite make sense.
When you design a video game you start out similarly but everything goes through many levels of build and revision. Nintendo in particular redoes things until they think they’re perfect. Tons and tons of unused assets lurk in their game codes because they redid a character, texture, etc...
Meanwhile, building for a theme park it does have this sort of refinement, but to a lesser degree. Once certain things happen, you have what you have. Like when they build the show building - the ride can’t get longer. They install the track and the ride system isn’t going to change. Pour the concrete and the basic shape of the scene won’t change.
So.. go to Nintendo with a plan for Mario Kart based off the early artwork that is solid enough to start basic construction. Anything that would fall into the “oh, well, we’ll figure that out” - like an effect, the timing of a scene, etc... will raise red flags and cause them to pause things.
Think of when Maelstrom was built originally. Ride length was argued between the various parties for budget reasons the whole time. In the end, it was supposed to have a shorter track but move slowly. Turns out, water doesn’t work that way, and the ride vehicles went too fast - negating planned scenes and dialog.
In a similar situation I can see Nintendo going “...but have you figured out the vehicle speed yet?” “Oh we’ll tackle that when...” “No. Figure out the vehicle speed and show us the script and we’ll decide if it meets our standards.”
Nintendo won’t have a ride that is 2 months from opening but the WiFi doesn’t work so the vehicles keep getting lost.