Valid points but the reality is that Obito didnt use it so you cant use it a vs thread
Going by that logic then kakashi didn't use it either so he can't use it in a VS thread. Obito's chakra possessed kakashi, the only things that obito needed were a chakra refill [which he got when he died] & a body. His chakra could've possessed any body & the result would've been the same. Obito used kamui to cheat death & he gave
his powers to him.
Examples : Madara obviously can perform Shinra Tensei but since he never used it in the manga we cant just use it in thread saying "Madara wins via ST"
Madara used deva path, the ability to control attractive & repulsive forces. You get all the associated abilities that come with it which includes ST.
Hiruzen can perform all jutsu in Konoha but that doesnt mean we can just say "Hiruzen will win via 8 Gates"
Hyperbole, it's impossible for hiruzen to learn certain jutsus associated with konoha [ex. gentle fist] so that claim isn't valid.
Obito was not the one inside the Susanoo and Obito was not the one holding the Kamui Shuriken
It doesn't matter, it was not kakashi who had the power to use susanoo, the kamui shuriken were not kakashi's.