I am just a pax: a pax who sat at 35,000'+, in the middle of the night, over the middle of the Pacific, in a 777 for the first time, and consciously re-examined my faith in the ETOPS calculations.
The question sounds a bit bush-lawery. That is, there is surely no longer any serious question about the practical safety of ETOPS, so the question is about the wording of the legislation. That is a question about legal interpretation, not aviation safety.
I am no more a lawyer than an aviation professional, but from a common sense point of view, it would seem that the law would be complied with if the reasoning went like this:
-We want to operate twins over the Pacific, because cheaper.
-We see your point, but our principal objective is safety. Demonstrate that you can do this as safely as flying the Queen of the Skies.
-Engines have got a lot more reliable. Here is a metric merde-tonne of calculations and a set of regulations, beyond what is considered safe for normal twin operations, that support our point.
-You have persuaded us that your calculations are sound, and there will be no diminution of safety, so you may do this, unless/until experience shows we got something wrong.
Experience would seem to indicate that the result has been no diminution of safety. The last time I had an aeroplane on my avoid list, it had nothing to do with the number of engines, and everything to do with the type of batteries.
Meanwhile, the corporate culture of profit-maximization as the first priority (in all airlines) has me more worried than the number of engines.