The SEC doesn't mind if you cancel a planned stock sale as an insider - 'no insider trading without a trade'.
It's an entirely plausible that there's "no speaking about a gag order without speaking".
Still, all theoretical and purely speculation, because as far as I know this has never been tested in court.
I do agree with the quotation though. I have a hard time believing government wouldn't somehow figure out a secret way to violate your first amendment such that you have no legal recourse.
Actually, they do tend to mind, and they will scrutinize you much more intensely if you engage in insider not-trading... it's just there's not much they can do about the non-sale in and of itself.