I am surprised that no-one has mounted a legal bid against the state, IMO there are some grounds that the state is acting unfairly:

In order to a device to gain CARB status, it should not be very expensive to go through the procedure, instead of thousands of dollars (where/who does this money go?) there should be a flat fee of $50-100, after all they smog test a car for $30 or so, why can't they test a car device for a similiar amount?
Its as if the state has a monopoly on CARB testing and as a monopoly charge obscene amounts of money for its "services".

The "fail if it looks different" sounds borderline legal to me, I can think of no other circumstances in law that wield such power over people with such an arbitrary "test".

I am very surprised that no-one has mounted a legal challenge to Californias smog laws.