From your link:
In March, in a bold “Oh yeah?” moment during an interview with the Washington Post’s editorial board, Donald Trump took the paper’s dare and revealed, then and there, his very short list of foreign policy advisers. There were just five, though he said, “I have quite a few more.” The list was a head-scratcher, a random assortment of obscure and questionable pundits. One of the names, offered without elaboration, was, “Carter Page, PhD.”
So, if the FBI had that, and Trump was denying this guy was with the campaign, then the FBI had good reason to keep the investigation to themselves.
Trump wasn't denying he was and advisor to the campaign.