Remember, it’s not the fall that causes damage/death, it’s the sudden stop at the end.
The quicker you stop the higher the peak g-force you experience, and that’s what breaks bones, etc. At around 20g’s the force is enough to rip the aorta free of the heart, which is usually fatal.
Ideally, if you must jump or fall from a building you want to land on something soft, “soft” being a relative term. Dirt is preferably to pavement. Grass to bare dirt. A dumpster full of garbage is better (unless, perhaps, it’s full of metal filing cabinents).
The OP estimate of 15m is overly optimistic. In general, the fatality rate starts going way up as soon as you reach 20 feet, or about 6m, and humans rarely survive greater heights.
That said - if you jump and land on your feet DO NOT hold your legs ridgid - bending of ankle, knee, and hip can absorb the shock to some degree although you are mostly definiately risking broken bones and spinal compression (the latter can be fatal). A belly-flop landing can also dissipate the impact, but only up to a point. The concept here is to slow the stop, or more precisely de-accelerate less rapidly.
By the way, the terminal velocity of a spread-eagled human body (the skydiver’s posture) is 120 mph, give or take a couple. Which, by the way, is not something you will survive without an extraodinary landing point. Falling feet first or head first considerably higher speeds can be achieved, but we don’t want to go in that direction anyhow.
Those who have survived falls from airplanes aloft or other great heights without benefit of parachute have one thing in common - something to dilute the impact. That might be dense tree branches, deep snow, or really anything that turns the sudden stop into a more gradual one. The stunt people in movies use this concept to break their own falls - falling from heights onto giant air mattresses or huge stacks of cardboard boxes and so forth.
The quicker you stop the higher the peak g-force you experience, and that’s what breaks bones, etc. At around 20g’s the force is enough to rip the aorta free of the heart, which is usually fatal.
Lateral movement (the suggestion of altering the direction of one’s fall, like a skydiver) only helps if the shift takes away enough of your downward velocity. It’s the downward component of the fall that kills. Even so, if you converted vertical terminal velocity of 120 mph to lateral enough to reduce the vertical to, say 20 mph (still enough to break bones) you then are traveling 100 mph laterally. Which means if you crash into something you still have fatal impact forces to deal with. Back when I was learning to fly I was told that, in an emergency landing, you need to get your lateral speed down as much as possible as well as the vertical component. In general, if you hit something in a landing airplane, horizontal speeds in excess of 80 mph are almost invariably fatal (and that’s with some metal and other structure around you to absorb impact). The emphasis is to get your speed as low as possible in all vectors to maximize survivability.
About those elevators - Cable hoisted elevators are extraordinarally safe - their safety bakes may result in alarming jolts but they can stop the fall of fully loaded elevator with total cable failure long before the fall becomes fatal. I don’t know the engineering details, but death usually comes from trying to leave a stuck elevator car and then falling down the shaft, rather than the car itself causing the death of the occupants. Hydraulic elevators are another matter - if the system fails you fall, it’s that simple. Last summer Chicago had several deaths and a dozen serious injuries when one of these failed, and those folks only dropped 2 stories. One survivor who escaped with minor injuries supposedly managed to get up on the handrail in the car before impact, but I don’t recall all the details.
