User blog comment:Omega natsu2/Chapter 387: Tartarus Arc, Part 4: Father and Son, Predictions./@comment-4829046-20140604151057/@comment-7418318-20140605082530

Well... that white Zetsu with Yamato inside it was a lot stronger than the completely grown ones, so there's a good chance that these Zetsu that are formed around Humans are also stronger.