Authors say that, in the United States, 99% of fire deaths occur in buildings without sprinklers, making that the key component of a safe building over multiple exits.

Article doesn’t mention that but it does mention that the vast majority of deaths come from buildings without sprinklers, most likely buildings built before a lot of modern building code.

Sprinklers + properly fitted fire doors are probably good enough for such small buildings to provide both suppression and spread prevention.