The description of those trumpet blasts in Revelation indicates that their effect would be noticed throughout the world. I hardly think that a talk by Rutherford in Ohio, or anywhere else, which was only heard by a few thousand people would be noticed by people in China or India, where I doubt that anyone had even heard of the jws in the 1920's.
It's just another example of the arrogance of the org's leadership in applying the fulfillment of bible prophecy to themselves, and one of the more bizarre examples at that.