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We need to know more about it, but it looks alright from what we've seen. I hope we have trainer opponents that can also use styles, or maybe that's something the red-eyed pokemon can do. Also, screenshots with some moves having style choice and others not makes me think you need to clear some prerequisite with a move to unlock the styles for that move, perhaps involving the requests. The Oshawott having strong moves early and higher HP than it should makes me feel a little strange, as this may mean we have another LGPE starter situation, but those starters also needed buffs, so that could be good.
I do feel like styles will benefit offensive pokemon more than defensive pokemon, though that might not mean as much considering passive pokemon always struggled more in single player due to longer battles draining more limited resources like items and PP.
I'm hoping there's no competitions for this because they're having trouble working out balancing styles and not for a lack of abilities or some other existing battle mechanics. Others have pointed out no abilities on the official website, but it's also worth noting that there's no abilities on the starters page on BDSP's website, just a twitter post pokemon made about the starters. Unfortunately, no abilities show up in the trailers and it cuts off at one point before a Rhydon would've taken recoil, but even then it could've just been Reckless instead. There's also the question of how no abilities would work with pokemon home, since I'm pretty sure meltan/melmetal still showed abilities in home when transferred from LGPE. It looks a little more likely there's no abilities, but it could go either way and I'm hoping they didn't get cut.