One oversight by the article: changes in household size.
[Edit: I deleted an incorrect paragraph about population trends in the United States; I had misremembered a regional trend as a national one.]
For example, even if the housing supply and population in an area stay constant, if fewer people are living in each housing unit you’ll get a shortage. Yet nowhere in the article’s numerical analysis is there mention of this additional factor.
This is not to say that landlords aren’t a problem, but the entire premise of the article is that based on population and housing supply trends the supply “crisis” does not exist, which without incorporating changes in household size into their calculations is simply not a conclusion you can make.