Yes it's a CO Bulletin, but they are issued with consultation from Boeing, often on Boeing's recommendation- I'd be surprised if most B777 operators don't have the same Bulletin (or at least similar) as anomalous fire warnings are a problem with the aircraft
False 777 cargo smoke alarms are not uncommon. This problem is not unknown. At least two incidents have happened here at my local port. I can't remember, however, if they were set off with high humidity or disinsection sprays. If it doesn't make the decision to evacuate more difficult for pilots, I'd be surprised.
Were there really no other indications of fire in the Saudia incident?