I don't know if this is true. Assuming this is an established practice by large companies, there would also be a cultural notion (by managers agreeing with the sentiment, CEOs, famous executives espousing it) that hiding your voting patterns means you are voting for the "wrong people". Plus, by going to the media, you'll be permanently known to any future employer as a rat on your company's practices. While this is good for society it has personal consequences to you.