Ok, let’s forget the trees or any scenery for a moment. Let’s say they don’t exist, and that the plane is in an open, and empty area.
Planes are very finicky things. If the angles aren’t right, it won’t be able to fly. If you look at an airplane wing from the side, they are normally shaped a bit like long tear drops. After gaining it’s initial momentum, the plane is kind of lifted by gliding through the air pressure. Plane wings are shaped that way to make the air move faster over the top of the wing. When the air moves faster, the pressure of that air decreases. So the pressure on the top of the wing is less than the pressure on the bottom of the wing. The difference in pressure creates a force on the wing that lifts the wing of the plane up into the air.
Airplanes are full of many things that are pretty complex. If we changed airplanes to be able to “roll over” for safety, we would lose that special system that allows the lift to happen.
Since planes are so finicky, planes with different purposes will usually be built differently. Since they still have to be able to fly, adding one thing may sometimes means removing another thing. Those particular planes were never meant to make those maneuvers, and they weren’t built to handle them. It would be like upgrading a car’s engine block to be turbo-powered, then keeping the same coolant system and expecting it to run fine. You have to respect the equipment and follow guidelines, as they are usually there for a good reason.
The idea was that everyone would know not to do that (via their pilot licence), and that it would be ok to have specialty planes. The plane was never meant to move that way, and the wings weren’t fortified for those angles.