I don’t know much about wagon’n’drags but this driver seems both skilful and rash to me.
If there isn’t enough grip then the situation is not one he could get out of himself.
I put this more in the category of playing Russian roulette and hitting a blank chamber, rather than a well planned manoeuvre.
Going the other way with a load of timber on is going to be ‘interesting’. 
I was assuming that he was turning around, before loading and descending.
Hope so anyway!
for his sake let’s hope it was a one-off bad idea that he “got away with” and not a deliberate plan for next time
Now you know why they call it a ‘dangler’. 
Had bigger than that round here before driver:-)
I reckon he’s done it plenty of times before and will do it plenty more times. There’s bug ger all weight in those trailers, the MAN will have a bogie drive and he will have the power divider and both cross locks engaged. It looks far more spectacular than it is.
I get the idea of it I think, but putting half a load on the truck, to put weight on the drive bogie would be a lot wiser I’d have thought.
The flexibility of the A frame type coupling provides a lot of scope for manoeuvres that you wouldn’t be able to do with the solid bar close coupled design or an artic.
In this case he took it to the extreme where damage to the trailer and drawbar could have happened.Lets just say that it he would have failed a UPS drawbar assessment test.
P iss that with a Chereau 
Might even have CTI (central tyre inflation) for extra traction, too. A good number of forestry rigs do now.
Probably he, and 20 others, do it 3 times each every day and the guy with the camera is sat in a crawler just in case someone gets stuck. In my experience most forestry work is well covered against mishaps.