Impossible to log out of Game Center
Game Center is toggled off on all my devices, yet, when I open a game on my MacBook Air, I get a pop up that says "[my username] is already signed in. You can keep using the already logged in cloud account or use another one." There's no "log out" option and you have to choose either your user account or choose a different one, but you cannot log out. Once you choose, it shows you're logged into Game Center.
Again, I have Game Center toggled off on all my devices, there's no where in the game itself to log out, and I can't find the app anywhere in System Settings, so I can't check to see if I can toggle it off there? So if I've done what I can to log out of Game Center, how do I stop Apple from logging me in?