For the case of "A transaction can of course be reversed simply by making the inverse transfer." the equivalence is broken by the technical authorisation requir

For the case of "A transaction can of course be reversed simply by making the inverse transfer." the equivalence is broken by the technical authorisation required - in most systems if I'm able to make a transfer, I'm not able to simply make the inverse transfer, that other person is able to make the inverse transfer. So the question of reversals essentially is whether the inverse transfer can be made (and if so, under what conditions) against the wishes of the original recipient. And when there's a good answer to that, the next question is what are the exact consequences to reversals (or attempted reversals) of money that's "not there anymore" - e.g. there's a valid transfer from A to B; followed by a transfer from B to C; followed by a need/decision to reverse the A to B transaction (which is a very, very common scenario in e.g. scam resolution). For systems that treat money as the conceptual equivalent of "stuff" (e.g. Bitcoin) that's a very hard question; most of our financial infrastructure (probably for millenia) treats money as the conceptual equivalent of "debt relationship" i.e. a metric of who owes whom how much, and then it's a bit easier but still not trivial.