A large enough increase in supply could cause property values to level off while also increasing the vacancy rate for rental properties. I think the idea is that those circumstances would make real estate no longer attractive as an investment.

Is anybody saying "just" in that sentence?

We do need more supply. We also need changes to existing policy to prevent what this article describes.

Both and, not either or.

I'll take the supply position. So much of LA is zoned for SFHs. Now they can have an ADU but that doesn't do much. We need density. We need to make it easier to build. That slows down climbing rents. LA housing is at a massive deficit.