Here we see the kyuubi is being taken over by Susanoo. Now I wonder if that is the reason there is a s perfect Susanoo since someone would need a lot of chakra. Madara is going to use the kyuubi as the median for PS and now it is Hashirama being used as a median.
Maybe thats why it was crucial to control the kyuubi from Madara's perspective, he didn't know he would have hashirama cells, and to fight needed his strongest Susanoo. Maybe this is how Sasuke and Naruto will beat Madara and thus part ways to fight again another day. Sasuke will somehow acquire.
Edit: Mangastream Madara says shatter and his Susanoo is performing a handseal