I think you may have misunderstood something. The fire marshall would have no way of knowing what type of pyro was used since the place had been totally consumed by fire. Yes, some do burn that hot. What they used is no different than sparklers, its like a "cold flame". It didn't burn the band members or anything else, except this foam insulation that is either obviously highly flammable or had been soaked in an accelerant.
I think when the fire marhsall made that comment he was answering a question about pyro in general. I may be wrong.