I think QANTAS would be treading a dangerous line to assume any refusal of a crew to extend crew duty was based on pseudo industrial action. I personally doubt that had anything to do with it.
I'm guessing that if someone did stand the captain down, they have no idea of how seriously (in my experience) aircrew consider the "to extend or not to extend" decision.
Management talk about "if you make a decision based on safety you have our full support" ..
Typically though when that decision is made, you get done like a dinner. If not to your face then behind your back.