And since they're really financial instruments, the buildings are still only half full!
While they might work as far as providing residents two routes out in an emergency, they do present challenges to firefighters [1]:
> Jack J. Murphy, a former firefighter, fire marshal, and current chairman of the New York City High-Rise Fire Safety Directors Association, has inspected some of these buildings and says they present unique challenges for firefighters. For one, the buildings’ small footprints mean very narrow scissor stairwells that can have five or more turns between floors. “What would that do to my hose stretch?” Murphy said. The compact size also means tight quarters for operation and medical staging in an emergency.
[1] https://www.nfpa.org/News-and-Research/Publications-and-medi...