Ok I'm just gonna share some thoughts I had after watching the treehouse demonstration again. First of all, there is definitely a day night cycle of some sort:
But there are some doubts. First of all these two images are 15 minutes apart, and in the mean time one villager house was decorated. When the demonstrator went back into Nook's home's, Lottie told her that it's late and you should save/write up your report for the day. Also, when she tried to use the amiibo phone in this evening/night state, it would not allow her. So this brings up the idea that you can only decorate one house per day, assuming that it skips to evening once you complete a house. If this is the case, then it means the game wouldn't run a real time clock, which because of animal crossing history, I doubt is the case, but it is a spinoff, so they don't have to follow the rules.
Another meaning is that you can only scan one amiibo card per day (to decorate their house, inviting them over seems unlimited). And since Lottie told you to wrap it up for the day, it might be the case that you can only decorate one house per day. But the question we have is whether this is an in game day or a real time day.
The alternative idea is that Nook's home's closes after a certain time (real time), and after that you can only visit villagers and buildings in town, you can't do extra work.
Anyway, it could be the case that the game that was played is not the complete version, or some other factor like that. This is just speculation but I thought it was an interesting idea.