A lucky guess most likely. The whole finding out your foe is your father thing probably goes as far back as ancient mythology.
I don’t think that article got any circulation outside the San Francisco area, or magazines like Starlog would have picked up on that quote and gone to town with it.
Given the later furor over Prowse allegedly spilling plot points on ROTJ that lead to the falling out with George, I doubt the flanneled one ever found out about this.