The video contains excerpts of tests burns that were conducted on a wood truss assembly and also a wood 'stick built' roof assembly. The test burns were not scientific and are not intended to discredit trusses; they were conducted simply to help educate the fire service of the dangers that trusses pose if they are exposed to fire.
Trusses have many good features. The issue the fire service needs to be keenly aware of is that they fail quickly when exposed to a fire. Granted most building codes provide a good degree of protection for trusses.
But the problem arises when the fire either originates in the truss space or, somehow, extends into it, thus exposing the truss to fire. And then, as Francis Brannigan so accurately stated, 'Gravity Always Wins'