It's not an applicable ETOPS Philosophy
Might have expressed myself poorly here.
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Looking more at the supposition that because a generator keeps tripping off line that there's something wrong with said generator - so "no problems, we'll keep operating that bird with the APU running until it gets back to home-plate and we can address it further". In this case the fault was beyond the generator and in the circuitry (bus-tie?) and tripped the APU generator off line. You've then got an FBW a/c enroute in IMC/at night with only one generator up and running.
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Is that acceptable? Is it survivable with FBW if that fault was to cause another event? Or do we/are we use(ing) an ETOPS style of philosophy and simply declare that "you'd have to be mighty unlucky for that last remaining generator to quit on you. Statistically speaking it just ain't gonna happen. We got the figures to prove that."
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Well I'd be prepared to debate the validity of any such statistics when it comes to a singular (non-redundant) electrical distribution system - no matter how many generators are hanging off of it and supplying it. It smells a bit unsafe to me - and not just because of the FBW nature of the named airplane brands. And just because we've been doing it for years doesn't necessarily mean that it's a valid philosophy.