AFAIK, they withhold information in pretty much every investigation, then make the information public after all the facts have been found. That seems perfectly rational to me.
Of course, once all of the facts are known and the investigation is over, then they should make all of this information public unless doing so would jeopardize an innocent person’s safety.
For the record, I have no tolerance for lying, particularly where the government (or any powerful entity) is concerned.