In BC, the Humbolt has to be used in the logging industry. Primarily it was financial, as the government stumpage is paid on the scale, and someone calculated that the conventional notch reduces the log value by 2% (a big deal, when the provincial cut is 70 million cubic meters).
The 2" step up on the back cut from the notch apex is to prevent the butt from sliding backwards off the stump.
Yup, plus the feel of having more control,
Pretty much the way I always notched,
Jeff