I am not sure what threw the loaded seats out, possibly the sheer force of impact. But I am not sure it was O2 related either.
You are quite correct, O2 does not burn, however it is an accelerant and will supporting burning through adbiatic compression and expansion. The rupture of a cylinder would leave high speed gas escaping though a jagged tear which would in most causes be enough to complete all three sides of the fire triangle. I have yet to see an O2 explosion that did not result in ignition of combustibles.
Not saying youbare wrong and it could not happen, I just don't think the damage matches a gas cylinder explosion.