My read between the lines of the Boeing
PR is the major source of toxicity is the interior panels of the aircraft.
Neither the aluminum nor the 787 outer structure contribute significantly except for the time to be defeated by an external fire.
My memory of such external fires is almost solely comprised of ground fuel-pooled fires.
An internal cabin fire is clearly another problem.
I am curious what a Asiana fuselage might look like along the fuselage top after the fire breaks through to inside the cabin, but that's just a structural damage question and not germain to toxicity.