It’s well known as “road block” airspace.
Why is it called that? Because it can act as a road block even in perfect VMC.
Twist it any way you want but the pilot was clearly forced to leave 6500’ on that track.
It is highly likely if the E existed they would both be alive today.
The ATSB report claimed that AsA are changing that C to E! Wonder when? Bit late for those two.
And he had two separate GPS units which showed airspace.