On a course like that, anyone without the 'skills' is very quickly going to be dropped from any sort of podium contention. DId look like cracking good fun (literally for one US junior who snapped his bars).
Amazed at the amount of riders that don't really seem to able to handle a few rocks!
I imagine if put into a pressure situation where there are thirty riders in front of you, and thirty behind you buzzing your tyre, you're going to feel a bit different about riding those rocks for seven laps while at max-heartrate.
I'm sure you're a real technical god on your 5" trail bike when you have time and composure to tackle stuff.