Hard to answer the why do it question and Im sure it differs from person to person. Why would soldiers still on active duty or former Vietnam era SF veterans want to dress up in WWII uniforms and jump with old parachutes from relic aircraft on historic battlefields? Same reason some civilians want to do it. Something to do for the experience I guess. A lot of people say it is to honor the WWII veterans who had to jump but I think most of us fall somewhere in between. Guess we could ask Dan since he is shelling out money and time to go through jump school this summer. As for me, Im a civilian but did a bit of programming for the Defense Department, got my pilots wings at Randolph AFB and further instrument training at Bergstrom AFB. Did some sport jumping but decided I wanted to try things the old way with rounds since it wasnt as common. Figured out how to jump with a leg bag using a reproduction British copy of the WWII pattern and placed two filled five-gallon water bladders inside to give me eighty pounds of additional weight. Dumb maybe but not dumb enough to carry it off the DZ since they could be easily drained after landing. I wanted to jump with my BSA folding bicycle but having a reserve interferes with the wartime procedures so never got around to it.
Funny thing that contradicts itself to me anyway is the jumping former military people in the two groups that hate reenactors. They also dress up and get kitted out to look like the troops did during WWII, but they insist that you cant reenact a parachute jump. So are the jumping reenactors actually airborne? I dont think so and really dont care. If I wanted to be in the military, Id have joined up.
Back on your question about the guy that had the compression fracture in his back, I guess stall would be a more correct word than flare just prior to landing a round. Essentially dumping some air by pulling the rear risers to stop forward drive. He basically flew the parachute into the ground as he seemed to otherwise have complete control. Legs would normally bend as you go in to the PLF like you said but this guy wasnt prepared to land and so hit with stiff legs which folded under his weight on impact. Being ahead of him on the jump, I was down a second or two before he was, roughly fifty feet in front and to the left when he hit. I got my chute collapsed and grabbed his as he was down and the chute was still inflated and I didnt want him to get dragged even though the winds were not out of our limits. The guy who landed behind him saw the impact better than I did and also helped to get the injured person off the field when he insisted that he was able to walk. He recovered for the most part but was out of work for three months.
You mentioned that military training jumps are called off with 15mph or greater winds. Our jump with Pathfinder for the Arnhem 60th anniversary was in high winds. The aircraft was really being hammered by the winds and many of us hit our helmets on the roof while hooked up waiting to go. The Dutch military called off their mass jump as a result of the winds even though they were airborne with seven filled transports. They cant justify injuries while we will accept them since we have traveled for the experience. Cant explain the logic as it is lost somewhere in the why do it aspect. One good thing about the PX4 is it practically collapses itself on landing when there is no weight on the suspension lines. The B and C chutes used in the US are almost zero porosity which can make for gentle landings but they can also re-inflate quickly on the ground.
Last thing I guess is the long fall the guy in Normandy had. One of his suspension lines had thrown a half hitch loop around the handle about halfway to the canopy. The position of the shovel caused him to be held sideways towards upside down and his body weight prevented him from being able to undue the knot. His canopy was roughly a third inflated which might be why he didnt react quick enough to the emergency situation he was in. He just kept trying to fit it. His reserve canopy fully opened but I guess in retrospect, it was due to the pilot chute pulling it out for it to catch air.