Right now it seems that one person has the game and he is the primary source of these screenshots. You'll want to watch Kaphotics/projectpokemon/whatever hackers since when they get the game they'll be datamining.
EDIT: Ninja'd 2x
RE: Dark gym, postgame: I'm repeating myself here but a lot of twitter guys seem to be parroting 4chan's anonymice or fishing for likes. For every real leak there's 1000 liars.
EDIT2: I can't even find a source for these posts.
Dark apparently comes from the same Spanish tweeter.
EDIT3: Lol
View attachment 203904
The English version of that tweet says "apparently".
They just catching all the info they can and passing it like a deranged Passimian. This is nothing but a random text leak. No source.