The exception to that rule was the 'stall the aircraft into the treetops'
Yes, and I agree, though the idea would be to stall in from level flight along the treetops, rather than descend into the trees fully stalled from umpteen feet up. When you decide to stall into treetops, I would presume that you have chosen your path, and perhaps aimed between the big trees. Otherwise, yes, fly as far into the crash as you can.
Take a C150 for example where the distance between your own back end and the bottom of the fuselage is only a couple of inches.
'More of a concern in a RG, the 150 has amazingly absorbent landing gear legs. The difference being that there is a crush zone of underfloor bulkheads between the belly skin, and the floor,
and the seat legs, then cushion, on any highwing single which comes to my mind. For those low wing types where you sit on the spar, particularly RG's, there is only seat cushion and very short seat legs to absorb vertical loads. When I was young, I was attending the Oshkosh airshow. I witnessed a Siai Marchetti 260 pilot deliberately enter a spin from only a few hundred feet up ('cause the announcer said: "he will now demonstrate a spin..."). He impacted in a vertical descent right in front of me, and was fatally injured. With the gear up, and hitting vertically, while sitting on the spar, only his spine absorbed the vertical load. We had to taxi past the wreck when we flew home that day - photo.
Note in my photo, the wrinkle in the aft fuselage, and flattened bottoms of the tip tank, along with absence of any slide marks whatever, to show how hard it hit vertically.
https://aviation-safety.net/wikibase/39240
