The Bureau of Statistics use the data recorded, which is what the doctors were instructed to put on the death certificates which was C19 if they tested positive.
When the ABS were asked in the Senate enquiry into excess deaths about that ruling, C19 positive test means C19 death, they tried to justify it by saying people with comorbidities were likely to have been finished off by C19 so it was valid. You would then perhaps assume that the same people being given strong opiates would have their cause of death registered as death by opiate overdose as it finished them off.
