and accept the descent rate on impact or try and judge the height and arrest the rate of descent by flaring at what may or may not be the right height above the ground
I imagine that this is something which is poorly, or never taught. I hope Big Pistons will see this and comment, I'm sure he would have wise thoughts. For myself, I'm going to assert that if you are unable to certainly establish your height above the surface you should not flare. Not flaring is not good, but stalling or spinning in is worse. You are better to contact the surface under control, faster than intended, that's the way the restraints are designed to work, and the video is evidence of that.
Interestingly, the other day I was removing a radio from a crashed 172D, in which there had been two "walking wounded" level injuries. I noticed that the pilot's inboard seatbelt attachment fitting was ripped right out of the floor. But I guess it absorbed nearly all of the forward crash force before it ripped out - so it did it's job, just with zero reserve capacity....