Yes quite correct, but that situation applies only to sealed stairways that have been classified as emergency escape routes, and fulfills all the criteria. ie, ...fire rated landing doors, landing doors must open onto the stairwell, doors must not allow substantial air flow past them when closed, all doors to be mechanically held closed (sprung/hydraulic door closers) Stairwell must not contain any flammable material etc etc...
These types of stairwells have a forced air supply to open roof vents, to a give positive air pressure within the stairwell that also helps to keep landing doors closed. All such systems can be over ridden by any fireman's control point...