The Humbolt is good for stems going to the mill. Also, western logging is dealing with large trees where even a "wedge" can weigh more than 150 lbs. The Humbolt makes the wedge sort of fall out rather than have to be wrestled out. It is good however if the tree has a lot of swell out at the bottom where the wedge can get rather large.
For the average weekend wood chuck, the traditional 45* on the upside is preferable in my mind.
The reason being is the wood cutter is always dealing with a mitigation of the saw's weight as a result of a downward or horizontal cut.
Also, a lot of "occasional cutters" aren't sharpening their saws to pro standards making an upward cut more difficult.
What is essential is that the wedge cuts should meet as exactly as one can muster.
Not doing so can cause a tree to hang and subsequently barber chair.