Very nicely done. Bet it will eat logs in a hurry!
We had a couple of those (commercial version - I forget the brand name). But instead if a blade like yours they had a piece of chainsaw chain wrapped around the drum in a spiral slot. We use them to grind the top of stumps that were too high in the ski slopes. Dynamite worked a lot better though.
Here in France this kind of tool is not available on the market. There is only a few log home builder. On the video it was the first try so the one who held the chainsaw used it carefully. But after, with the habit, he used it much harder and it worked very well. It eated a log very quicly.