I think your info on the baenschi is wrong, Male is not looking for a more suitable female, because the already spawned twice.
They are, as you called harem breeders.
As for my cockatoo, They are acting like your description of baenschi. There were two females in the tank but both male and the female attacked third female viciously way before they spawn, so I had to seperate her.
My conclusion is these are living things, so there is no black and white wtih their behavior. Once in a while there will be ones that behaves differently than the general population.