The GPS correction codes are classified. No one knows what's actually in them. So, why does everyone say they prove Einstein's theory of relativity is true?

I've noticed a strong tendency in dealing with the theory of relativity, and Einstein in general, to simply assume that it must always be true. And, all the evidence in favor of it, takes this form. This evidence proves the theory of relativity, because it must prove the theory of relativity, because the theory of relativity must be true. This is, actually, a classical logical fallacy according to Aristotle -- Tautology -- saying something must be true, quite simply, because it must be true. It is commonplace for everyone to claim these days -- but, most particularly, physicists and engineers -- that the GPS locater only works because of Einstein's theory of relativity, even though none of these people actually have the slightest idea how the GPS locater actually works, because the coding for it is highly classified information. And, indeed, if you point this out to these people, they see no problem with this at all! They will simply claim they "know" that it incorporates Einstein's theory, because, it has to! Does the absurdity of the Cult of Albert Einstein know no bounds, at all???