Spoiler At that point, it really stops being a capital ship and literally just becomes a space station with guns and propulsion. Not that the idea of Snoke taking refugee in a flying city-castle is that bad, mind you. Kind of fits his paranoid characterization. It also fits the idea of Snoke having that as his capital for what's still a more militarized and seemingly utilitarian government like the FO; there's no palace world like Coruscant for him to rule, so instead he chooses the most ostentatious and ludicrous display of power and wealth he can while still maintains the appearance of usefulness of his home in wartime. And while I still think the Legends Eclipse SSD is a better overall design, making it appear wider rather than longer is a good way to communicate its size in quick shots in film.