Is that a US think? I've worked for employers in several European countries and have never heard an employer telling me not to discuss pay. Once a manager told me not to tell everyone about a pay raise as it was out of schedule and he didn't want lengthy discussions with other employees. But that was his personal request, not a request by HR. If I had wanted to discuss it I could've done without consequences, he made that clear as well.
It's still unusual to discuss pay in many companies but not because the employer prohibits it.
It's still unusual to discuss pay in many companies but not because the employer prohibits it.