Board Thread:Naruto Discussions/@comment-25139119-20140905185119/@comment-3048523-20140913103437

This is surely an erroro of continuity by Kishimoto, however I believe that a simple explanation could be related to what said by Riptide240 here:

Riptide240 wrote: But when Naruto and Sasuke seal her, she loses the ability to control chakra

After that the Yin and Yang powers act on the Juubi, actually it lost the ability to control the chakra and fight, so already losing the battle even before to be trapped in an artificial sattelite.

Even if speculation, IMO is not farfetched to think that Hagoromo and Hamura could have decided to leave the Chibaku Tensei process in a middle way, sealing the Juubi (and so its "Gedo Mazo" hunk) inside the first instead to leave that the technique could end to complete itself.

Later, in his old age, Hagoromo would have unsealed the chakra of the Juubi from himself, giving so the birth to the nine Bijuu.

Finally, in the end of his days, he could have decided to unseal even the body of the Juubi left in him for making the rebirth of the Juubi the most unlikely possible: so he would have removed the Gedo Mazo from him and left that the Chibaku Tensei jutsu was terminated, sending Juubi's prison on the space and transforming it in an artificial satellite. Of course all this with Hagoromo dying in the end for the loss of Juubi's life force kept in the Gedo Mazo.

I believe that a similar scenario could explain everything and at the same time keeping the right importance to the panel of Hagoromo and Hamura in parallel with Naruto and Sasuke (that would show always a scene depicting a Chibaku Tensei performed on the Juubi and that ended to determine its defeat in that past' situation as much as in the present of the story).

Off Topic but if there is something that appear to me more hardly explainable is how Hagoromo was able to fight the Juubi, and then to seal it in himself, without ever to notice the presence of Kaguya. Maybe he misunderstood it for the Shinju's will how did Madara? Or maybe he has always suspected something similar considering that he didn't seem surprised for Naruto and Sasuke fighting his mother (and after all, very likely for Hagoromo his mother was suddenly disappeared in his life time, something that could be pretty suspicious for him).