Seems like optical illusion; the slope seems more pronounced when viewing from above. I’m sure few of our Muni guys can ride that trail.
“Sheer” madness! 
I got dizzy just watching!!!
From some of the other videos it doesn’t seem so steep.
https://www.youtube.com/watch?v=KYlI1hLDBbY
It’s a bit funny that this quadcopter video went so nuts, it seems like lots of people have ridden it. Including these two guys and their dogs.
Yeah, I’m sure from the quad copter cam PoV , or viewed from below, it looks insane. Sorta like looking at how a cow or a sheep manages to hang on top of a steep hill or cliff. I dont see them struggling to hang on…
I remembered when I was way young and just begun to learn how to ski. I looked up on the white capped mountains and was totally in awe. Mesmerized of the fact of that theres tiny specks of skiers actually able to come down from there, and not actually tumbling down like they were supposed to. Who’d knew, less than a couple seasons later I was on the very top lift of Heavenly Ski Resort doing the same thing.
So, i guess, from a distance, it always looks scarier, because you dont see the less steeper ledges to traverse upon, your eyes sees it as a whole, mind blowing steepness, from a distance…
still never the less, it takes lotta nerves and confidence and completely zoning out.
On the other hand, from the helmet cam it never looks as steep. Not sure exactly the reason, but Im sure its alot scarier in real life, standing looking staight down, than the POV of the hemet cam.
Im sure the some of best unicyclists have the confidence for this one. No problem. We have tons of traction and control downhills. For sure, if I had only one to choose from. I’d much rather do it on a uni and lose my wheel, then on 2 wheels and trying for the life of me to bail out head first! : )
Here is a video of a guy riding downhill at Sedona.
You can see he carefully chooses where he makes his descents.
I can see plenty of places where an unarrested fall could lead to serious injury or death.
Must be a hell of a rush to ride.
Jim
If you look at the horizon on the top left of the screen 1.07, you will realize that the camera is slanted causing the hill to look steeper than it actually is. 
Although if he were to drift off line he could end up slipping down over a sharp drop…waaahh
Michal commented on Strava, that he thinks it is not possible to repeat that on unicycle, but I guess it seems also not possible on the bike for most of the people. He also wrote that we can always try 