I believe there's no way in California for the kind of worker on Tesla's factory floor to be considered exempt, so he would almost certainly be getting overtime even if salaried. You could easily meet the 2x minimum wage annualized pay exemption, but the "administrative/executive" exemption would be an absurd stretch. A few people might meet professional exemption but probably not most of the workers, and the ones that do are likely already salaried. (I'm not a lawyer, particularly not an employment lawyer in California, though.)