I've not been following this thread closely. Is that height official or a guesstimate? Obviously Coronado is getting a tower but what I've seen for CBR isn't nearly as tall.
Just a guess. Mostly a worst case scenario. And based on the idea of being able to see the Illuminations show on top of the lake clearly. If the plan is to see just the fireworks, the viewing lounge can be much lower.
Also, to manage expectations. If I create a low building in the mock ups and the real one is much taller, people will be shocked. If I put a tall building in the mock up and the real one is much lower, people will rejoice. I don't want people yelling at me because I set them up for a short building and it's not.
Also the outline of the building is the outline of something in the the permits. It could be, AFAIK, the outline of a pool/pond and not the actual building(s). There has been very very little confirmed about that building.