However, decisions made by identical twins (and other systems with shared inner workings) aren't independent. Not because of some kind of spooky backwards-in-time-causation, but because both decisions depend on the genetic makeup of the twins - which was jointly determined by the mother long ago.

Then again, in the chewing-gum variant of the smoking lesion problem, your decision whether to chew gum and your genetic propensity to get throat abscesses aren't independent either. But everybody would agree that choosing to chew is still the right choice, wouldn't they?