It isn't a typo, and it isn't decoration.
c — catastrophic haemorrhage. Lowercase because it isn't a step in sequence like the others. It's an interrupt. If you find life-threatening bleeding, everything else stops until it's controlled.
Direct pressure → wound packing → tourniquet. Reassess continuously, because controlled doesn't mean permanently controlled.
The reason it sits before Airway at all is simple: someone can bleed out faster than they can obstruct. Order matters, and this one earns its place.
Full lesson in the Primary Survey classroom.