Don't be so sure of that. In this business, you want to through everything to your advantage and that sort (maybe 2") strip of vertical wood that needs to get broken takes a good bit of force. That may depend on species, but either way will add significantly to the force needed to trip a hinge on a big tree. Now does that add to the force or is it a force multiplier?And, this actually leads me to the conclusion that the vertical bore in this case isn't that critical, as that is in a very weak plane anyway - the consequence being that the rear vertical face of the hinge will form as necessary, just as it does on any other back-cut not having a vertical face bored into it. Yeah?
Then how much does that added force effect a fall? And in exactly what real-world way?