I'm sure there are exceptions and as we all know, what a cm tells you isn't always true.
Our reservation was at 11:30. We stopped by at 11 and was told we couldn't check in earlier than 15 minutes before the PS (this is probably because they don't actually open until 11:30. At any rate, we just hung around for 15 minutes and then checked in.
I asked the CM for a water view. She looked at my PS and said that there were 13 water view tables and that all PS's for 11:30 were guaranteed (the word she used) water views. Once those tables were filled, they quit booking for 11:30. She didn't make any notations on our PS card at all about a water view.
At any rate, we were the first to check in, the last to be called (we were getting a little worried and actually counted the names called...we were 13th). Every other table seated at that time was a water view.
Also, we made our reservations through vacation planning 2 months before our trip. When I told them I wanted a water view, they also said book for 11:30 and while they wouldn't guarantee it, he said he was quite sure we would get a water view.
Who knows, but as crowded and crazy as it was, if I wanted a water view, I'd book for 11:30.