Board Thread:Naruto Discussions/@comment-38187233-20190117103621/@comment-25122992-20190117114127

Ten-Tails can be Ten-Tails only when Gedo Mazo is the vessel for all tailed beasts' chakra. Sasuke used Susanoo as a vessel instead, so it's not Ten-Tails, but, as stated, Susanoo filled with all TB chakra.

P.S. There's a Naruto questions wiki for such questions.