it’s that you are attacking very specific peripheral claims

I'm countering the claims you're making. I'm not going to intuit your arguments. If you want to clearly state your argument in its totality, I'll address it in its totality.

Your original claim was:

The real issue is not that current landlords are exceptionally greedy (the rules of capitalism assume and encourage everyone to be as greedy as possible), it’s that there isn’t enough housing stock to give everyone who wants one a unit.

The article you linked above did not support this argument, as it said the majority of people in that age range living with their parents are doing so because they don't make enough money or don't want to give money to a landlord, not that there isn't housing available to rent.

The fact that you're trying to exclude houses that are available for rent (presumably for prices that people can't afford) from the above stated numbers is yet another example of moving the goalposts because, based on your original stated argument, those should be included in the discussion.

If you narrow your argument enough times, you'll find something that's not easily countered - obviously. "There's 20 million people who want to live in Manhattan, but there's not enough units for them!" would technically be correct, but it's a worthless argument to make. Yes, some people will end up living outside of their ideal best case scenario, but you know what? I think getting everyone into houses is the first step, and we can work on improving the location of those houses second. Someone who's unemployed and unhoused in LA could be unemployed and housed in San Diego and their situation would be immensely improved.