What do you mean by just a hub? There's obviously quite a bit more going on here than the equivalent hubs in the last Splatoon games:
-It's huge: you can see a map that shows you'll be moving around to various islands around the big rocket and you can actually see these areas in the background in the gameplay, so I suspect it's one whole seamless area without loading screens.
Other stuff from the gameplay:
- Definitely a melding of idea's from the Splatoon single player games (focusing levels around new weapons and mechanics) and Octo-expansion (the way the levels are framed with challenge built into weapon choice and limited attempts, and the starting waiting room).
- Usage of the little buddy for various things, like attacking and distracting enemies.
- Looking at the map, there are at least five main areas before getting to the rocket.
- On occasion, some kind of meter popped up that had a silver badge like image on it. I'm not sure what that could be for. It might increase when you do certain moves or specific tasks.