That's...not how law works. The law doesn't adopt a different meaning in litigation than it has in administrative application; when the Court adopts an interpretration/operationalization of the law (which is what adopting a “test for use in litigation” is), it defines what the law is. That's true in general in common law systems, and it's certainly true in specific in that administrative application if California State Law is controlled by how that law has been interpreted by the State Supreme Court.

Making the legal regime more resilient against future change in the composition of the Supreme Court is a thing, whether it's something that justifies the effort expended or not, it's really not my place to say. But AB5 did not substantively alter the status quo legal regime faced by Uber, etc., so any change in practice they shot was not driven by a change in legal regime stemming from the law.