"total involvement", or confaguration, is what matters true. However fires are more complex than that. Generally the wood frame isn't a source of fuel for the fire until later. The carpet and other furniture that is the same in all builds is likely to burn first. Not long after the wood frame is burning the steel frame absorbs enough heat to fail - but either way you really want to be out long before it gets that bad (and probably are dead if you are not)