Board Thread:Versus Debates/@comment-1872728-20170111185046/@comment-35622277-20170114231352

It was never stated that he ever lost the chakra from the other Tailed Beasts, we only know he lost the Yang mark on his hand that was necessary for the Six Paths seal.

Judging from the fact that Sage Kurama mode was very much enough to deal with Toneri, and SPSM Kurama was enough to deal with Momoshiki with the help of Sasuke (both of whom got destroyed in a matter of minutes), I'm pretty sure he just deduced his final form was not needed.