It's a not a myth if you're in the SF Bay Area. Other parts of CA are terrible. As you've pointed out it's both smoggy and hot. Coming from FL where there are only two seasons, I call Bay Area's weather "air conditioning" weather. It feels like you're in a really nice climate controlled building, but outside with sun. That said, it's not going to last with climate change. Air quality is already taking a beating with all the forest fires, and it's getting hotter and hotter. Pretty soon, it'll be no different from what people think of today as SoCal weather.