Dani and Christian’s relationship throughout the film is strained but for me personally, I think seeing a real contentious fight between the girlfriend and boyfriend could add to the arc of their relationship and would help enforce Dani’s decision at the end of the film.
I can definitely see where a scene like that would be beneficial.
The director said he never could have imagined that he would cut this scene until he did, so the extended cut presumably gives him an opportunity to put it back.