For Japan to have been delayed/stalled like it seems to have been, it almost has to be a ride system/engineering issue that affects all of the parks. Pivoting Orlando from Kidzone to Park 3 wouldn't directly affect Japan. I want to say there was mention of a ride system delay on here, but can't recall if it was a legit rumor or just board conjecture. If they did indeed come across a problem in the MK ride system during R&D that would require changes, stopping all construction makes sense. Don't want to pour footers just to find out a month later that they need to be moved somewhere else. Depending on how significant the changes would be, that could also be part of the reason that they'd move from Kidzone to Park 3. If the building needed to be bigger, maybe it wouldn't fit the plot as is. And if you are going to have to redesign the whole plot anyway, moving to a new spot isn't as big of a deal.