The companies I have experience with had huge monorepo. It's not unimaginable that everyone inside the company has access to some important code, what usually they don't have access to is customers' data which has few more checkpoints. They mostly considered the code commodity, you could take it and still couldn't compete with them. In fact, this is one of the core reasons, some companies are hesitant in going all remote. No one wants their questionable code to be leaked.