I am guessing that he didn't want it to fall down the hill. I think they where cutting it into fire wood and didn't want to pack it up the hill.
To me it looks like his cuts lined up good and then he cut the dutchman into the left side on purpose and then cut the left side off on purpose. The guy with the axe did not know what he was doing and told him to stop as he was cutting the left side off. Ax man was then told to get out of the way and let the faller do what he was doing.