From the page itself, "A modern auto paint shop emits volatile organic compounds (VOCs) during primer, base coat, and clear coat application. The Bay Area AQMD makes permitting a new paint shop nearly impossible. This is THE classic example of what you can't do in CA." This point is trotted out and reframed multiple times on the page but it's literally self contradictory. It's not something you can't do in California, it's something you can't do without approval in the Bay Area Air District.
It's not a good place to be doing such an activity, as the area already can't successfully keep the air healthy enough to stay within federal limits due to environmental factors that trap particulate low to the ground. If you're at all familiar with the area you know concerns about air quality are not overblown and. Go further away from people or meet strict VOC regulations if you absolutely need to be doing that kind of work in the area, seems completely reasonable to me.
Existing shops get grandfathered.
See also the counterproductive legacy of the anti-nuclear movement.
Some guy’s website claims with big red scary graphics that this stuff is banned and these poor downtrodden business owners can’t operate.
I can’t imagine that nobody has opened an auto body shop in California in the last decade or two.
When it comes to businesses like large factories opening up that’s more of something that often gets approved on a case by case basis.
E.g., we can’t just say that the Chicago Bears are banned from building a new stadium in Chicago just because they aren’t willing to pay the costs required to do so and aren’t willing to meet the city’s requirements to get the approval vote they need.