The ridiculous thing is this seemingly was ready for the most part like, last year. They are only waiting for Fall to debut this so that the whole middle plaza gardens, communicore hall, and Moana debut at the same time, which will likely be right around when the new fireworks show starts.
Doing that all at once provides a larger media hit for them than opening piecemeal in their eyes seemingly because there's really no reason it can't be open today.