My guess is there is far more here than meets the eye. No doubt the Judge is fully aware that the Sussex Police are under intense pressure from the public to bring some sort of criminal prosecution over the deaths of eleven people. Consequently he is being (possibly) over cautious in not allowing the police to gain direct access to highly sensitive information.
The various results from both of flight and engineering tests could provide significant evidence which in themselves be could be sufficient to bring a prosecution of some kind.
On balance I think the Judge did the right thing.