It appears that the "management directive" has now been incorporated into the operating procedures for Brisbane Centre. Additionally, it has been determined that these restrictions on direct tracking do not override pre-existing allowances for direct tracking contained in ATC local instructions. As a result, more direct tracking will be given away, even if it is unsolicited. What routes/times of day are affected depend on the local instructions.
Alot of back and forth has taken place on the air with queries and explanations of if or why direct tracking is available or not. This increases the workload of both the pilot and controller, and can interfere with the use of R/T for others in the airspace. It has also served to increase tensions in an environment in which they should be minimised.
There are a multitude of reasons why direct tracking is or isn't available at any one time, and a controller is not always going to give a reason. It's made even more complicated because direct tracking will be available under some circumstances. Second guessing each other's requests/motives can only lead to an unsafe situation.
Pilots concerned with controller actions in these matters should talk to their management who should talk to ASA management. That is where the discussion of policies should (and should have) take place.