> because developers mostly would build high-end units This is such a frustrating perspective.
It's frustrating because, as propaganda, it's been extremely effective. If you're an opponent of increased housing supply in California, you can roll out that talking point whenever threatened. It's tested, emotionally resonant, and most people don't have the time to be explained why it's wrong. Supporters of increased housing in CA need to come up with their own powerful rhetoric, rather than whining about the fact…
In fact, a huge development project is going on in the downtown area currently. One of the requirements of the project was to set aside a certain percentage of the new units as affordable housing. When the developer was asked about the affordable housing at a city council meeting, they revealed they were targeting a price point of ~$1600/mo for a 1 bedroom. For context, the going rate in the city for a bedroom is $300-800/mo. There was no language specifying what exactly affordable housing so they can get away with it (something the city is working on for next time).
My point is, this is a real problem. You need to think about it and you need to actively prevent it in from happening in whatever legislation you put forward.