Please, re-read before making threads... It's because he didn't have full control over the Juubi, we saw that many many times, Madara has the Juubi on a ****ing leash making it his *****. He can do whatever he wants as the jinchuriki.
this has been discussed so often. Obito was probably talking about his phasing with kamui where he sent pieces of his bodies to the other dimension to avoid attacks.