User blog comment:Omega natsu2/Chapter 368: The Third Seal, Predictions./@comment-7418318-20140122130704/@comment-7418318-20140122152703

That "swirly one" was completely supressed by Obito ever since he saw Rin die, but now that Obito is almost dead, it regain control of their shared body. So it's not really like he was forgotten, just that he was unable to speak.

I think this was just Kishi's way of showing that this is the Zetsu clone, rather than Obito controlling the body, rather than any synchronization with the anime.