If you're on an ETOPS flight and you're over the Atlantic or Pacific, then you would have to be extended overwater (which is simply greater than 50 miles from shore). ETOPS certification requires aircraft equipment that meets or exceeds the extended overwater requirements, so it's sort of a moot point. If you're on an ETOPS flight, the extended overwater ops is already covered.

However, there are many flights with extended overwater that don't involve ETOPS. Cutting across the Gulf of Alaska between ANC and the US west coast. ANC to Asia on the NOPAC routes proximate to Russian airfields or even NAT tracks that are far enough north to be close to Gander, KEF or maybe Greenland.

Unless your fleet has a mix of overwater and non-overwater birds (which has bitten some flying to ANC from California), there's not much to the extended overwater ops.