Masteria Preview?

I really don't see how those examples are any different.
Why wasn't the barrier mentioned before now?

Your complaint is especially ironic considering your signature
Do you peach every time a new Pokemon generation comes out?
Because I know for a fact that they never explain how hundreds of species could have been completely unaccounted for for so long.

Mentioning a barrier after the fact is still better than "OMG GUIZE A NEW AREA HAS JUST MAGICALLY APPEARED INTO THIN AIR"

And yes, actually, I do have a problem with new Pokemon generations. I'm sure most Pokemon fans have mentioned at least once in their lifetime how they find it funny how new Pokemon just magically appear; especially with respect to the baby Pokemon. Pokemon is hilariously flawed in many ways concerning its continuity and storyline, but who gives a damn? It's fun. Maple kind of NEEDS a story for it to be respectably fun.
There's a reason IsaacGS' story thread got so much attention. The story in Maple is one of the only good things these days.

And for your thesaurus link: synonyms don't always mean the exact same thing. They could have a similar concept, or mean something similar, but one will always be better used in certain contexts.