Perhaps the only rationale (not that I necessarily agree with the outcome) is that California imposing such restrictions violates the interstate commerce clause

Perhaps the only rationale (not that I necessarily agree with the outcome) is that California imposing such restrictions violates the interstate commerce clause. The test involved does not consider intent, only whether or not out-of-state businesses are disadvantaged because of state law. So if (e.g.) bespoke carmakers have problems selling to CA because of this then it is a discriminatory law. This is potentially permissible (in contrast to the Hong Kong holding company vs. Australia suit about cigarette packaging) as the functioning of the US is predicated on states that can work together despite their regulations. Note how states must recognize each other's wedding certificates and driver's licenses, for example.