So Dick's basic proposition is correct, in the genesis of EROPS/ETOPS/EDTO, all accepted (whether it was right or wrong) that long range twins were not "as safe" as a three or four engine aircraft, but they were "safe enough" --- and "absolute safety", "safety is our first priority" and the present CASA selectively preferred interpretation of S.9A of the Act did not get a look-in.
Perhaps that was true 30 years ago in Australia, I'm not in a position to know. But I was involved in the development of EROPS/ETOPS rules with the FAA in that same time frame. No such provision was made about 'safe enough' - either it's safe (per the one in a billion requirement I posted earlier) - or it's not safe - in which case it's not certifiable. That some groups objected is immaterial - that's an emotional response, not a technical response (not unlike the two crew/three crew flight deck debate)
EROPS/ETOPS rules were developed using technical statistical methods - the same statistical methods used for showing every other critical system on the aircraft is safe. It's also used for an "Equivalent Level of Safety" (ELOS) - when a new design doesn't meet the letter of the regulation but meets the intent of the regulation the regulators can grant an ELOS finding (ELOS was heavily used when EICAS was incorporated to replace all those flight deck lights and dials - and was needed when Boeing incorporated the thrust reverser 3rd lock after Lauda - 25.939 says a deployment in flight must be controllable but with big fan engines that's no longer practical, so Boeing was able to obtain an ELOS by showing the 3rd lock was effective in making sure an in-flight deployment wouldn't happen).
Further, IIRC, while Qantas was an early adopter of EROPS (for flying over the Australian outback), Australia's initial EROPS rules were based on the
already existing FAA EROPS rules - rules that had already shown to be just as safe as a quad.
Besides, this whole crusade overlooks a very basic fact. As per my earlier post, current ETOPS twins are statically meaningfully safer than the quads and tri-jets they replaced. By that metric, allowing ETOPS has actually made flying
safer and hence saved lives.