They mean the keys and Dream World stuff which held about half the story of Black and White 2 behind this obscure system that isn't explained to you and is completely skippable. There's tons of cutscenes only accessible with online connections. They're important and without them, BW2 is pretty bland story-wise. Chances are you never saw them. Not only were these not accessible, easily skippable, and obscure if you didn't know about them you can no longer access them. Also, I appreciate a hard mode and easy mode but what was the point of locking them behind beating the game? Who on earth wants to play Easy Mode once you already beat the game?
Contrary to popular opinion, I don't like BW2. I much prefer BW. I also don't like the PWT that much. I think it's a great idea but not letting them use full teams unless you do doubles is criminal. I don't want to play doubles. I never liked doubles. Doubles makes the game not nearly as fun. Instead of this chess-like match, you're never really in an unwinnable position in doubles. Triples? Triples are fun. But I never saw the appeal of doubles and why it's competitive standard is beyond me.