There couldn't be a day one patch that blocked new Pokemon, that would make no sense. Unless they somehow put one in and allowed all reviewer's copies to bypass it in some way. But there's no way they'd do that, and the dataminers will have everything ripped and posted by the week before launch most likely. If you want to stay spoiler-free just stay out of leak threads, or stop looking up anything about S/V in general, it's really the only way. It's how I did it for Elden Ring, and it worked pretty well.