Our OM A says to consider a re-route should an ETOPS ERA fall below operational minima; note “consider” and, depending on circumstances, it may not be possible to do this. As others have said, it’s a probability thing, much like going below critical fuel for a bit near an ETP: you didn’t plan for it, but on the balance of probabilities, you are very unlikely to have a decompression along with an engine failure in that short window, and there are things you can do in extremis to avoid running dry before you get to an alternate should the worst happen...