I often make requests under freedom of information laws in different countries. An argument you sometimes get back from government agencies that don't want to give you information is called the mosaic effect. The argument is that the information I have asked for is innocuous, but if I attach that piece of information to other pieces of innocuous information I would end up with a result that would actually be quite harmful.
The argument I am making in this circumstance I think is somewhat similar. The disclosure of the occupation of a requester within a department or between departments or two central agencies may seem by itself to be innocuous, but put together with other pieces of information in the public domain, it can have an effect that undercuts the right to privacy, and that also leads to undue delays for certain kinds of requesters.