Why would any of these people leak information considered to be of a damaging nature to the McCanns? Why not leak something a little less contentious? Why do you struggle to believe the PJ would ever do such a thing? It's not like it would have been the first time would it? All rhetorical questions which I don't expect you to (be able to) answer.
Well a Leicestershire police employee may have because he was sickened to the stomach with the thought that even though Madeleine had told her mother and father that she and her siblings were crying while left alone and still her parents left her the next night.
One of their friends might have because of the havoc the circus the McCanns had created was having on their lives ( perhaps it was the same friend who released the 'F**k off ' mobile phone footage of Gerry to the media ).
Or even Mitchell himself to deflect from the spectacle of the Rogatories and to justify their and their friends reconstitution refusal. You said it yourself , why would something so damaging be released especially by the McCanns ? That is exactly what a clever PR man would want the public to think.