Hm, there could definitely be something to this. The prospect of all-out brutal street brawls with dozens of Pokémon coming at you in quick order doesn't quite match the tone of the trailers so far, but then again, we never saw the Noble Electrode fight coming from the first Legends Arceus trailers either.I'm going to give a counter-argument.
You need to think outside of the box.
Legends Arceus isn't an exploration game. It's a collectathon with Mobile Game Quests. The map is there simply to spread out the Pokemon and then you find them and do mobile game quests, usually repetitive, in order to complete goals and Level Up. That is something that could easily be done with levels like these small Wild Areas in Lumiose City.
For instance, the Distortion Rifts in Legends Arceus are some of the tightest bits of gameplay since for a short while you can accomplish basically every major part of the game loop, plenty of rare Pokemon (some of which exclusive here) and constant battling, catching, rare items, etc. From a game design perspective, if you wanted to focus in on that addictive loop rather than exploration (which seems feasible to me), skipping the more open world and just stripping it down into essentially areas where those are constant seems pretty reasonable to me.
Where Legends Arceus was about catching, clearly this game actually is about Battling. Defeating Wild Pokemon doesn't come at the cost of failing to catch them, and we see that battles can go very quickly with short clips of Pokemon being defeated fast. With the camera angle and the speed of this ARPG combat, these small areas could easily become chaotic arenas with the player running around fighting new Pokemon as they spawn and getting items and more.
Legends ZA doesn't need exploration to follow the game design of Legends Arceus. Because all Legends Arceus is is a skinnerbox dressed up in an open zone. And I say that as someone that likes it. The only purpose exploration serves is to find where the Mobile Game Quest NPCs are and repeat the actions on them until you've finished your real goal- crunching numbers and making for a satisfying report sheet with dozens of tasks completed in one session.
I was also thinking that the game could be more story-driven as an alternative to exploration. The official site suggests you will be tackling all sorts of incidents, after all. But then I had a hard time fitting in the gameplay loop of catching wild Pokémon, which you will presumably be doing by the dozen at some point. It's not like you could feasibly rush to a crime scene to investigate, only to be met with the task of catching 20 Fletchling, or something like that. A story-driven approach like that would be more at home in the Detective Pikachu games, rather than one where you are explicitly playing as a Pokémon trainer.