> they likely told the same story to numberous people, so they are used to repetitions, but they have no (good) mechanism to detect when they tell the same story to the same person.

Maybe, but then there was that person I was close enough to, that I knew for a fact I was one of up to three people she told some of the stories to, and yet I'd still hear those stories repeatedly, on a weekly or monthly basis. So at least in that one case, I feel she must've adopted a completely stateless approach to conversation. As in, there wouldn't even be an attempt to recall she told me that exact same story just a few days before, much less that it's at least the fifth time I heard this within last 6 months.

I guess "having your heart on your tongue", as 'teekert puts it, would be an apt description. It's only now that it clicked for me that this is, in fact, a viable approach some people might have naturally adopted. Maybe it's even a superior one, as it keeps the state in the relationship.