It seems to me that a second engine failure is unrelated to the first or it isn't. ETOPS is based on the low statistical possibility of a second unrelated failure occurring.
A second related failure seems likely (not certain, but likely) to occur within a short time of the first. If so, a suitable airport 30 minutes away may be as useless as one 330 minutes away. (And, of course, something like a fuel problem could affect 3 or 4 engines as easily as 2).