I'm sure the Husky owners manual show that cut for leaners, dang I had it somewhere and even posted about it ages ago somewhere with pics.
There was even video, it's around the Husky camps and Swedish logging camps.
The cut was used primarily for forward leaners. Two side cuts were made to provide a point like a triangle, then the back cut. Idea being the point was in line with where the tree would fall and the back cut was a slow release. Not used on big trees.
Trees do tend to naturally weight a side or sunny side, if felling volumes in order it can be like dominos, same if felling with say a tail wind.
I'd say the fella was doing that, 2 side cuts to point where to go and then a back cut, no real hinge just some torn timber toward the front of the triangle and if he hung around the cut may have cut it off for a flush stump/butt.