Read Greg Child's article on Grovelling.
I'm a groveller. While mountain terrain chaos sometimes is so crazy it literally makes me sick to my stomach... I have an ability to move rapidly over chossy, moss, brush, scree, talus, snow, blah blah particulary in the down hill direction.
I think being a skier helps. I think being a telemark skier helps even more. Having a reckless streak probably encourages it. I once ran down a 500 foot scree slope miles and miles from the nearest road, AFTER a forced bivi at 13+k with no bivi gear (long night) wearing a pack as my more cautious and more careful footed partners looked on in horror and spoke in quiet terms over whether I was suicidal or just stupid.
Just reckless I reckon...
But I can throw caution into the wind and GET DOWN the mountain forthwith.
In Child's article he speaks of grovelling and used a climb he did with Lynn Hill somewhere in Himalaya - she smoked him on the climb but when it came to the descent she was simply too careful footed and too unnerved by the chaos of the typical high mountain environment. If you read her bio, she explains where this reluctance comes from.
One observation - some people can't see well enough to know what it is they are stepping on, real time. So they have to go much slower and actually feel the ground before committing to each step. This is the slow crawl of death for someone like me - takes them an hour, literally, to do a slope I can grovel down in 10 minutes.
Grovelling has its down side, like when you step on a giant block, it breaks loose and rolls over your leg, crushing your calf muscle. I hate when that happens.