Juubi Jin true power unlocked with Sage Mode?

[Megatolium]

We all know how the Juubi is said to have "immeasurable Senjutsu Chakra" thanks to Naruto and partial stories of Kurama.

But why didn't Obito or Madara use it? The same chakra that's shown to shoot a Bijuu Dama with its explosion reaching the heavens.

Instead Obito has to partially release the Juubi to shoot Bijuu Dama's, unlike Naruto who does it otherwise.

Does this mean one need to access Sage Mode in Juubi Jin mode to access its Senjutsu Chakra?

 

[Your Creepy Stalker]

Because they need something to form the Bijuudama with. Thats why Naruto couldn't use the Bijuu Dama in KCM.
That's why Obito patly manifested the Shinju to use the 4 Bijuudama.