I think the effects analysis is wrong; SF's policy does squeeze out all poorer newcomers and anybody who falls on temporary hard times, while letting the wealthiest in at any time. There's a reason that studios were going for $4k/month until the pandemic, and it's because the price was getting set by a tiny tiny fraction of the highest incomes, since those were the only people left.

So populations that had a lower home ownership base and less access to high income jobs, such as African Americans, have seen their populations completely destroyed in SF, starting exactly when SF decided to downzone.

Rent control is just fine for newcomers, as long as tenants don't ally with homeowners to keep our newcomers. The tenants lose in that battle when it comes time for the next generation to find housing.