There was all types of information, trip planners and photos of it during that time. If they didn't know it, they were not paying attention. All of us at one time or the other have arrived at the parks when our favorite or interesting attraction has been closed or covered with canvas. It's too bad, but really, not avoidable. If they went because it was the 25th celebration, then they knew before they got there, if they didn't know then even back then that was a serious glitch in paying attention to the place that had an Icon so important to them that they didn't get to see it during the entire year+ it was expected to be there it ruined their trip. It went up before, during the construction and came down pretty quickly after it was planned to be down. I'm sure it was a big let down, but it wasn't overcomable and I don't think it was nearly as many people as you might think. What did happen though was enough people complained and whined about it even if they didn't really care and had seen the castle a couple of billion times, that we no longer get those big expensive highlights. I don't blame them for not doing it anymore, but it is part of why the parks are so damn dull now.
I think that this particular argument was mostly made up by people that didn't like the concept and thought it was to whimsical for their conservative ideas of what a theme park is supposed to look like. So let's make up a different reason, because that one, if it existed at all was only a minor problem and happens whenever a change is done. Most have no special time frame, this one did and was widely advertised.