That's bizarre.
I never knew there was a NRSA dress code, and I have traveled more than 95% of passengers for 25 years. Proceeding from this premise, it seems to me, having worked in a uniformed service in a former life, who (of the audience, because a dress code presumes an audience) is going to know? You're either in uniform or you're not. When you're not, no one knows you from a hill of beans. And, given the collegiality reported above, why would a GA want to enforce it -- e.g., rat out an employee or family?
Of course I'm not doubting the story. I just don't get having a dress code for this. Tell employees never to be out in a partial uniform, period, full stop. Because that's disrespecting the uniform. (Though I always see dead-heading pilots without their bars on their epaulets.) (And I don't have a problem with it.)