Once there is an official profile for a game prior user profiles can’t be used anymore unless you rename the game’s .exe. That might look like an unnecessary restriction to you, but ease of use and a lower chance to mess things up for less experieced users had to ranked higher in this regard than total freedom for pro users.
BTW: You can trust me when I say that you don’t want to use any other profile for Far Cry Primal than the official one. Neither has a potential user profile DirectVR support nor any shader fixes (provided it supports G3D at all).