I was referring to the sloping back cut... lots of idiots like to put a steep angle on the back cut thinking that it will prevent the tree from going over backwards... it won't, but the angle does make driving wedges easier, up until the hinge wood shears off and kills yer pick-em-up truck...Not sure which scenario you are addressing - the deep face or the sloping back cut. As you know, gravity doesn’t help you on a face cut unless you are cutting compression wood or you have converted the back cut compression wood to tension wood, or severed it and supported it; both of which require some mechanical means - wedge, tension line, jack, heavy equipment, etc. If your compression wood is in the back you have to move the center of gravity forward - a deep face gives you less leverage with a wedge thus making it harder to drive - like starting in second gear. Also like 2nd gear, the stem will be lifted higher with each movement of the wedge. So theoretically, a deeper face requires less wedge height to get the job done but requires more force to get it there - and as you noted it makes things more dangerous - bust the hinge when the center of gravity is still in the wrong place and it over. Nothing here you don’t already know, but maybe some don’t.
as for depth of face cut, meh, its a matter of how hard its leaning, and how much room you have for wedges, sometimes a little tree you want a small face just so you can bury the wedges all the way.
does a shallow face help banging over a back leaner? Seems that a deeper face works better? but as for the physics of it I'm not sure.
In truth I think it has more to do with how hard its leaning, if I think I can just wedge it over, its not leaning real hard (lazy remember) so I make a deep face cut, giving better hinge/counter weight activity. if its real hard leaner and needs a jack, I'll make the face shallower mostly to provide plenty of room for jacks and wedges etc.