Tank34.
There's a verse I recall, one can't place new wine in old wineskin. I think that would be quite apt over here in this situation. Now, be that as it may, here's what i feel is the issue. Oil properties change with heat, friction and whatever else that goes on in a transmission. Over time, it loses its whatchamacallit 'the lubricating properties' and on a molecular level, it would bind together to form another substance which would fit into the nooks and crannies, gasket etc located on the transmission. now i assume when a flush is carried out, it would take with it these little molecules which are by now hardened into little pieces which good or bad might be stopping some leak, cracks etc arising from the neglect of the transmission by its previous owners.
So, as to the probability of your second paragraph taking place, i'd say yes it could very well be possible. the thing is unless one has purchased the car right off the showroom, it would be rather difficult for a subsequent owner to know exactly what sort of maintenance was provided during the car's lifetime prior to purchase. it would be advisable to maintain your ATF once every 40K kilometres travelled.
speaking of which, i'm about to hit that marker........
