if i were designing the game, i'd definitely create "related culture groups" that could and should be subdivided to the point of insanity. Each minority group should be represented, no matter how pathetically insignificant.
Because if that's not the way it's designed, then this forum is going to be full for months of threads that don't focus on the actual game play of v2, but instead focus on "why was <minority x> not represented in <province>!!!???"
that will distract from the discussion that will actually matter.
It has already been stated that cultures will NOT be divided a ridiculous number of times, since it wouldn't add much to the game, and would be a micro nightmare. An example used was, what if you had a province that was a real melting pot, and you had dozens of cultures there?
It would be incredibly difficult to figure out who is happy/mad at you, and more importantly why?