In James Maguire's biography "Impresario" he says Sullivan fabricated the airport story. I haven't got the book so I don't know if he says why.
I think this might be the why you’re looking for zipp:
“ The London Airport story makes for a flattering portrait of Ed: in a moment of serendipity, the veteran showman, always looking for the next trend, spots a rock ’n’ roll band perched on the cusp of international fame. But it’s highly unlikely that Ed was in London Airport on October 31.”
It goes on to cite evidence for this, mainly what Ed had written in his newspaper column around the time he was purported to be in London. The story seems to have made its debut four months after the Beatles appeared on his show for the first time. I don’t know if he’d been planning to say it or just made it up as he was being interviewed by an unnamed reporter. But he liked the story, and repeated it more than once, tweaking it at times. It wasn’t a complete lie; it happened but he wasn't there to see it.
It seems that Peter Pritchard sent Ed British press clippings about the boys. I didn’t see Bob Precht mentioned. When Pritchard learned that Brian felt the time was right to invade America he urged Brian to hold off and let him try to open the door to Studio 50 which, of course, he succeeded in doing.