Well the 9 tomoe sharingan's design is the regular sharingan+rinnegan. So the way I see it, that eye possesses the sum total powers of both the Sharingan and Rinnegan.
When Hagoromo was born, he only obtained the Rinnegan aspect, and then from there, his son gained the sharingan aspect of the eye.
Again we don't know what powers Kaguya had aside of Bakugan and Sharingan.
Like I said, she ate the fruit which possessed all of Shinju's chakra. So theoretically, she should gain all of its powers including KKG.
Best way to put it, is that the rinnegan and sharingan are two sides of one coin. That coin is the 9 Tomoe sharingan.