When you buy sharinnegan with fcs, you get it as a new skill, after, using sharingan and hatake steal your sharingan, sharinnegan still on the list, as the rinnegan
why would you buy sharinnegan in the first place , if you're going to get Obito Eyes? Well that would be the player fault not the game's thought sharinnegan is also divided by sharinnegan and rinnegan and since obito can get rinnegan , u get rinnegan as a doujutsu