So, I want to bring this up, but Theme Park Obsession's recent video shows quite a few changes. I'll post the video first, and then go from there, but to say they are going slow is..probably not the wisest call? Atleast not in the way we are seeing it.
The first large change of note, is on the side next to the Mario Kart showbuilding, in that, it looks like they added another layer of primer or paint onto the buildings. It looks a lot smoother now, much more firm in color and the edges look more curved.
Notice the one to the top left, next to what seems to be one of the power stations. The shaping of that wall contrasted to the one in the middle, in guest-accessible areas. You can also see the blue paint also present, but I doubt that'll be there that long.
The other major change, lies in Bowser's Castle. Of note, two things are present:
Of note, closer to the bottom you can start to see the same grey paint being present elsewhere, starting to trickle into Bowser's Castle. It looks to be in a solid stripe, going from one end to the other, being stopped only by the more defined and present smaller archway (As opposed to the large crescent above that (Which I am guessing is going to be the top piece for the mouth, for it's connectors and what-not).
The archway a bit closer:
The last change, is also on Mt. Beanpole, in that grey tarp we saw a few days ago. It seems to be staying, and looks to be of a heftier fabric, perhaps to protect whatever is currently in place for the time being?
I might be grasping at straws, but hey, speculation in this case might actually be a really good thing to do, especially in deducing how close we might be to prefabrification installation. Many thanks for the update, TPObsession, it's certainly made my night more interesting.