The Parking structure being done early could be able to accomodate staff and operations working on the projects going on, along with having an overflow space for guests with bus transport if needed to get people to UONorth.
As for the water park, that's more going by the assumption of the possibility of the Waterpark being an later incentive to be added for later on. They don't need a two-park pow wow for the first year of the south, and it may make sense to hold off until they can withhold the capacity.
Back to Scott, the only change I would say, is the hotel and CW opens early, with the park undergoing a two month period of softs (meaning July would be the proper opening). I doubt they are going to have a Volcano Bay scenario of not being open until right before people leave, and it'd give incentive for test-adjusting to occur with the general consensus.