I love this, a great example of highly skilled craftsmen. The principle of this kind of Japanese joinery is 'working with nature as opposed to fighting against it.' There are buildings in Japan 1000 years old that are built using these kinds of joints that are essentially earthquake proof.. The wood is allowed to swell and contract freely according to the ambient moisture levels.
However, that is not to say we in the West have got it all wrong. Modern adhesives and techniques have certainly changed things - vacuum pressing, epoxy resins - even PVA glue - allow the wood to move. I just appreciate the ingenuity of the joinery displayed in the video.