I agree that it should just refer to the southern area, and it's possible that as SF has hollowed out and doesn't have nearly as many tech workers it will retur

I agree that it should just refer to the southern area, and it's possible that as SF has hollowed out and doesn't have nearly as many tech workers it will return to that definition. But it's not just tech firms — sometimes law firms and other types of companies will open an SF office and call it their "Silicon Valley" office.