If this doesn't sound bad enough, it's possible that Copilot is already enabled. As we know this kind of features are pushed to users instead of being asked for.

Maybe it's already active in our accounts and we don't realize it, so our code will be used to train the AI.

Now we can't be sure if this will happen or not, but a company like GitHub should be staying miles away from this kind of policy. I personally wouldn't use GitHub for private corporate repositories. Only as a public web interface for public repos.