To be fair, the people planning reservations have to coordinate with the amount of people in their party. Whether it be family, a tour group, etc, that number of people will not be anywhere near the number of people Disney needs to coordinate with to get projects off the ground and completed.
If you already know about this then I apologize for preaching to the choir, but changes happen last minute in the business world all the time. Something can be planned for months and then right as it's about to happen, get pulled. Likewise, there could be no motion at all on something, and then the people in charge of that thing are told they need to have it done within a month. River of Light is a prime example. Disney suits wanted it done by a certain date, they announced it, then had to pull it for technical difficulties. You have to ask yourself, would everyone be upset with River of Light if they didn't announce it at all, and just ended up pushing it back from Summer of 2016 to Fall of 2016?
Typically it's best from a public relations standpoint to not announce anything until you are absolutely, 100% sure, that it's going to happen. Under promise; over deliver vs over promise; under deliver. Looping back to my first point, sometimes you aren't sure something is 100% ready to go until the literal last minute. Lots of money go into this stuff, and to have something ready to go, but hold off for 180 days (to match with ADR) just is not realistic.
I wholeheartedly agree with you, it makes planning difficult and frustrating, but the amount of people Disney pushes in and out of the gate every day requires the amount of advanced planning we do so they can be appropriately staffed the day, and I'm sure it ties into a million other things that we aren't even privy to.
In an ideal world, projects/refubs/closing/etc would be announced at least 180 days prior to the event actually taking place, so we (the guest) can plan accordingly. Unfortunately there are just too many moving pieces of the mouse to make that possible.
