It is not so much as the axe, rather the type of wood used. You can easily hear how dry it is and looks to be knot free. Some wood species like this splits very easy.
There are other videos on YouTube showing a person splitting wood the same way but with a regular axe.
I would like to see a demo using some different wood such as oak that has totally different characteristics when being split with an axe.
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Earth and sky, woods and fields, lakes and rivers, the mountain and the sea, are excellent schoolmasters, and teach some of us more than we can ever learn from books.
John Lubbock