Duzer basically broke that belt. Chain would not have worked either in those conditions but more importantly, he just did not know...so his actions will surely change next time. What he did with the belt should be taken as an education but IMHO should not sway you away from getting a bike with Gates Belt drive.
Duzer was in a very stressful situation and that led to the mistakes that broke the belt. Some of his videos are entertaining but I Like Cyclinabout for info on internal gears and belts. Alee went near 20,000 miles before he snapped the belt on his Rohloff equipped adventure touring bike. As I stated before the belt braking problem has more to do with the improper mounting and tensioning by the bicycle owners. I like the advantages the belt has to offer and any of the so called disadvantages are not applicable to me.