I just run across an interview of John Lear by George Knapp from back in 1987 when this whole topic was much fresher in people's memory. He mentions a
few details such as this happened in 1964, but was given to people in 1972 for a show to be aired in 1973. Then watergate happened and they decided
Americans would think Nixon was trying to use this to draw attention away. So, they decided now is not the best time to do this. I have the link
positioned to this exact discussion, but if it plays a commercial, jump to 7:35.