I'd say the title omits an important context. Let's see how it looks like if I add a few extra specifiers..
"The poor are better off when we constantly build more than enough housing for the rich."
The last paragraphs actually point that out, albeit in a slightly reversed manner. As long as high-end housing supply is continuously being satisfied, the more aged buildings become affordable even without 95% percentile incomes.
On the other hand, I do find it somewhat insulting that the figures assume a time window of 50-60 years. This kind of approach ignores a crucial externality: if it takes ~3 generations of neglect to see the problem, it also takes another ~3 to repair it. Even assuming a perfect 180-degree flip in housing, zoning and transit policies, that's a century lost to bad decisions and blind greed. And in the meanwhile, the city is pricing itself out.
I'm not a historian, but I sure would like to know a bit more. Has any great city survived 100 years of exodus?
It's only misleading in the sense that it would better to say "The poor are better off when we build more housing of any sort, even if they can't afford the units being built."
It's not misleading. It makes some assumptions of the reader [that the context is housing and that given constrained supplies, the pressure on affordable housing is eased when more market rate stock is built for those who can afford it --i.e. they have other stock to choose from].
Like when you go to the grocery store before a holiday, many people will tend to buy the leftovers [constrained stock] they normally would not buy --so it is with housing.