FWIW, I have been asked, "Do you know why I stopped you?" It happened in Newton MA on a radar setup on a main drag through a residential neghborhood. I answered, "Probably for speeding." I got a warning ticket. Don't know whether that was for honesty, or because he was mainly set up to give warning tickets, or some other reason. I also don't know what my speed was.
Last time I heard from an LEO, LEOs in MA could find out whether the registered owner had a permit, but they had to ask for it, and generally didn't. I have also heard from at least one MA LEO who thought that people who volunteered such information were a little off, and were usually trying to say something that the LEO really didn't want to hear.