@Ummmm
//Some people use the accusation against their partners to control them even though they don't really think it's happening.//
I don't understand how being accused of something you know you haven't done can exert control over you. You know it's false so you shrug it off. Then you hound them down, to try and discover why they've set out to drag you down when you've done no such harm to them.
Then you leave, because they are possibly psychotic, on top of being manipulative.
I was going to suggest paranoia, on his part but irrational thinking is usually full of holes and someone as smart as a therapist would be alert to that. He somehow has The therapist convinced of enough things about his partner that merit "remote diagnosis" and treatment "for her behaviour".
Manipulative, persuasive, dictatorial. Not a good mix. Add charm/charisma and you get…