Yes, the denial of 1975 is incredible. In 1975 the current GB would not have had any expectations of rising as high as they have. The old order was supposed to end.
When the governing body became the Governing Body in 1971, the 18 members were just picked by Knorr and Franz, to add to the 5 wt corporate officers. All of those original 18 are dead. The longest serving member now is Loesch, since 1998. The method for picking new GB members is no more legitimate than it was back then. They basically scout the world to see if there are any deluded men in the branches, COs, or missionaries that claim to have been hearing voices. Then they invite them to HQ, observe them, and see if they will fit the club. Holy Spirit has nothing to do with the process.