Because if Bill and Hill were actually in personal contact, Huma would never dare make up a LIE that Bill had decided to cancel the speech. She would worry that Hillary would say to Bill, “honey, why did you cancel the Morgan Stanley speech? I really thought you should go ahead with it!”
The ONLY way that Huma dares to propose such a lie is because she KNOWS that Hill and Bill are not in personal contact. Otherwise it would be suicidal for a staffer to tell one spouse a lie attributed to the other spouse.