that all depends on location. you guys out west dont use much other than the humbolt, while you would see very very few of those up here in the north east. most notches your going to see are the open faced, or conventional, and a boring back cut to go with it. thats the way the GOL is teaching, and also CLP classes.
The main reason for the Humboldt in production cutting is to maximize the scale. Other kinds of undercuts might work better in individual situations but we're used to the Humboldt and know how to finess it to get our lay and save out as much wood as possible. Logging is about production. It might be nice to have the time to turn timber falling into some kind of art form but our main focus is getting a lot of wood on the ground...safely and effeciently.
That GOL stuff is fine I guess but they seem to teach that if you just follow all their rules and procedures the tree is guaranteed to do exactly what you want it to do every time and without exception. Thats foolish thinking...and damned dangerous besides. Trees don't go to school and they don't read books and they're sure as hell not impressed by a lot of technical thinking and fancy procedures. They'll do what weight and gravity and force tell them to do. Most of the time. For the other times, stay light on your feet and be ready to scramble. That GOL book won't do you a lot of good when it's smashed, along with you, under a tree. Read your lean, watch the wind, watch the lay, don't run out of gas in the back-cut, and have a pocket full of wedges ready. And don't be ashamed to run like hell if the situation calls for it.