Bet that tax return guy never thought a stranger would read his W2s 37 years later.

Ran into almost the same thing on a big water oak with root rot last fall. What worked for me was leaving the hinge way thicker than normal, like a good two inches on a 30 inch trunk, and then boring the backcut so I could feel how soft the middle was before committing. The rot was mostly on the tension side, so the thick hinge held long enough for the tree to tip past the point of no return instead of snapping and twisting. If the base is puny enough that you can push a screwdriver into it, roping it off from the start is the smarter call, no shame in it. Wedges help too but they won't save a hinge that's already mush. Glad nobody got hurt, a fence can be rebuilt.

Scale wins, scoops are guesswork.