Where is that data from? I'd like take a look.
These numbers go back to very early poultry science -- from before commercial operators had forced-air ventilation and the various mechanical aids to keep hens raised in intensive confinement alive.
Here is a 100-year-old book to look at: https://www.backyardchickens.com/threads/poultry-for-the-farm-and-home.1443907/
Raising layers packed together like sardines requires force air ventilation, mechanical aids to dispose of their waste, and practices such as debeaking to prevent cannibalism.