It’s not cross-group. Bonobos fight with other bonobos. Intergroup conflict is settled with sex instead of violence, it’s about group cohesion.

Example: Human pisses off their neighbor. The “advanced” human approach is to take it to court and allow the whole to decide who was in the wrong. The chimp approach is to just beat the shit out of your neighbor and take some food from his fridge to rub salt in the wound. The bonobos approach is to fuck his wife, his daughter, and his son, to which his only response will be so mad he’ll fuck you then everyone is happy because sex.