Kirk here. I found this rather extensive article worth the time it took to read it. In a nutshell, the technology referred to in the title involves (1) identifying the rocks that need to be returned to specific locations and (2) enhancing the strength of the reconstructed walls while remaining largely faithful to the original construction methods.
Technology helping rebuild fallen Kumamoto Castle walls | The Asahi Shimbun: Breaking News, Japan News and Analysis
KUMAMOTO--Left devastated and in ruins by a spate of strong earthquakes seven years ago, iconic Kumamoto Castle is rising from the ashes.