I remember when the green NWT came out (as a teenager) I was under the impression the writers had access to the Dead Sea Scrolls. They were a recent discovery and it made sense to me. I dont recall it ever being said at an assembly or from the podium. I am pretty sure I heard it in the car while we were going door to door.
Now of course, I know different; no Jehovah in the dead sea scrolls either.