Either there is a leak, and that would mean that the American ambassador - according to the official transcript - really said what he is quoted as having said. That would mean that Mr Kurtzer lied when he denied the quotes. Alternatively the quotes published in YA were made up someone who knew or didn't know what was really being said at the closed meeting, and then it could not be considered a leak. Considering that the Foreign Office - that knows what was said during the meeting - is talking about a leak, the first possibility seems most probable.