Fully locked out full susser is then not a full susser, so the comparison would be lost.
Nothing i could see in that vid warrants rear sus in my mind......in fact i would say a hardtail would be an advantage compared to an 'active' rear end..........but saying that, it depends on the design and shock.
Some full sus xc bikes can give you more 'dig in' traction on climbs as well as down the trail.
But an experienced ht rider knows how to alter his weight to do that anyway.
No nothing too extreme there,( but it depends how fast you want to do it all) looks similar to stuff i and others used to ride 5 mins outside my back door in Mid-Wales.