I can't help but wonder what exactly burned on these balconies. I've not seen a balcony on this ship, but have on others. OK, there could be deck furniture that might burn. There might also be teak or some other kind of wood flooring that might burn. However, after seeing the photos with indications that the balconies melted, I can't imagine teak flooring or wood/cloth furniture generating that kind of heat.
And while it's certainly conceivable that a lit cigaret could have caused a fire, I'm going to wait until we get some official answers to this before I believe it.
Don't the SOLAS regulations dictate that room furnishings (i.e., bedspreads, furniture, etc) be somewhat fireproof? Isn't there a sprinkler in every room?