I don't understand the exfiltration part here. Wasn't only the user's own conversation that got copied elsewhere? That could have done in many different ways. I think I'm missing the point here.
They did not intend for their previous conversation to be visible to an attacker. That's a security hole.
Maybe that conversation was entirely benign, or maybe they'd been previously asking for advice about a personal issue - healthcare or finance or relationship advice or something.