Well its kinda like 4th Generation. Giratina was just a normal legendary Pokemon you could catch in D/P, but in Platinum, Giratina was used in the main villian's plans. Same goes for Black/White. Kyurem is just a regular legendary you could catch, but he was then used by Team Plasma in Black/White 2, which was a sequel to the first Black/White. Hope this clears things out.