I noticed the article didn't mention why we enclose staircases. (It's to prevent them from becoming chimneys, and to provide a safe place for disabled individuals to hide.)

They kept talking about saving money with fewer staircases, but the floor plans shown were all for 1-3 units per floor, which doesn't sound like "affordable housing" to me. It shouldn't be too hard to collect rent statistics for single stairwell vs multi-stair buildings in the same city.