Question (**spolier**)

I don't know, i guess the point is that whether Leo is gay or not doesn't really matter, what matters is that they found the family unity that they desparately lacked, remember in the beginning of the movie the mother expressed the thought that she was more upset about his sons being away from her (family falling apart) than the fact that two of her sons are gay, so I suppose that the focus of film is on Sabine's involvment in the family to get the family together again, not so much making Leo like girls, that was not the main focus.
As for Leo's sexual orientation, i guess it's up to anyone's guess.