Most shonen gives preferential treatment to the MC via fights, power ups, etc but it's spread pretty equally in Hunter x Hunter. Like sure all the Strawhats are the protagonists in One Piece for example, but Luffy easily gets the most focus of the group, same goes for Goku and Naruto, Ichigo. But Gon and Killua are kept at similar levels all throughout HxH. They get the same amount of characterization and development. One does not get more spotlight than the other. Kurapika now has his own arc with those two absent. I'd say Gon is not the sole protagonist in the same way other shonen protagonists are because he isn't favored in the story any more than his friends.