I presume that Candlelight Processional weekend will have the "funky" parade route, in which some floats are removed, and the parade route is from "iasw" to the Central Hub, where all the floats are placed on the road circling the Partners Statue, and then they return to "iasw", since Main Street is blocked off with the viewing areas for the Candlelight shows. It isn't perfect, but was the best idea that Disney could come up with to deal with the issue.
As for what is happening on that speicifc date, it could be as simple as a special after hour party for a park sponsor that is not announced to the public.
You have logistic issues during Grad Nights, and why Disney has made many modifications over the years to try and keep the park as many hours as possible, but still stock everything. It was a lesson learned in the early years of
Disneyland, and why Disney World was designed with more backstage areas and routes, including the Utilidors.
As someone who was allowed to attend special 3rd shift events for special guests, it is amazing to see what happens from park closing to opening. It is a big dance, and more than once has required the park to delay gates opening, especially on rope drop days. One requirement of these events is an escort at all times to make sure safety protocol is followed, as you just can't walk down the street, when the truck with airline baggage carts come travelling down the street. (It is a great system where they can sort items per location, similar to loading a specific airplane with the right luggage, backstage and then have a quick delivery in the early AM).
Now the Star Wars Land logistics are fairly easy, since there is easy backstage access. Things like work on the on-stage Rivers of America area, or Critter Country work might require the current operating sidewalks to be used to move equipment after hours could cause a change in the evening activities.
These things are usually designed for slower days to lessen the impact.
