PS; Outside Australia, a vast number of airline pilots would not have a clue what kind of airspace they are in, at any particular time, the fixation is an Australian "thing".
Just made so much more sense when it was simply "CONTROLLED (CTA)....UNCONTROLLED (OCTA)....or GAAP".
Maybe more emphasis in training could be given to teaching that requesting a clearance through CTA is not such a difficult or daunting task.....demystify CTA if you will. I know that back in the day I found the CTA "stuff" overwhelming, and have no doubt that some PVT pilots would still do.
Whereas I was somewhat petrified to enter CTA back then, I am now as equally concerned, or more so, to enter UNCONTROLLED.