The point is that there is a surge of baby-boomers who will die and the number of people younger than them are a significantly smaller group, so there will in fact be a surge in available housing.
This argument is missing the point - the questions is not how many people will be of age X in 2040.
It is about how many homes will be released due to owners passing away in 2020 vs 2040.
The very fact that there will be more older people in 2040 also contributes to getting more homes released.
What the statistics does not even consider is what happens if we manage to extend life, even by say 10 years. A completely different picture emerges where homes get even more expensive.
There's a precedent for this: schools. A lot of towns had to build out to accommodate the boom, then deal with declining enrollment for GenX, then another increase for the "echo" generation that we now call millennials. If you want to know what retirement homes will go through, look at what schools already did.
Today, there are ~77 million Americans over 60. In 2040, there will be ~100 million Americans over 60.
You can play with the numbers here. https://www.populationpyramid.net/united-states-of-america/2...