Is that a law in California? My understanding of the labor law is that California protects employees, so that if they sign a contract assigning IP to the company (which is almost a sure bet today, but not a law afaik- please correct me otherwise) they are actually protected such that it only applies if:

- using company resources, such as time, hardware, or office space, unless otherwise stated.

Clearly the case here, but my understanding of this law doesn’t align with how you described it.