I don't understand the arguments that they are "lazy" for taking this approach when they did rock work on the entire interior of the volcano. It's not like they just left all of the steel beams visible. Also this way avoids a major disco yeti broken aqua coaster situation.
Also I think everyone is missing the point of why this park is going to be special. People love the Disney waterparks because they are the best themed in the world. Volcano Bay will not be. However, while the Disney parks have only moderate quality collections of slides, VB will have a top 5 collection of slides AND and top 5 theming. that combination is what is going to make this special.