The spring theory is really the only theory that answers the 'why' part of the equation. I mean, in the presence of a high pressure spring, it would be natural for people to kind of just stumble upon a building technique like this. People would first make a pool by laying rocks to form walls, then they will start making the walls higher, then realize that they can use buoyancy to lift heavier rocks. Then engineer comes along and realizes that they can make a huge building, and thinks: 'why not?'