Nia Sioux isn't interested in rehashing her days ... including Maddie Ziegler and Mackenzie Ziegler. "I feel like for people from the original team, we went through so much," Paige told E!

Nia Sioux is sharing her side of the story ... dancers Maddie Ziegler and Mackenzie Ziegler also opted not to participate in the reunion special, and their absence was widely discussed.