I think you're right, the author doesn't cover those collaterally affected by secret information. However, this is outside of the author's main point.
The author is focusing on the principle privacy is not just about secret keeping things secret. Your example of people who may collaterally affected falls under this category. It's just an example of using the word private to equate secret.
The author is focusing on the principle privacy is not just about secret keeping things secret. Your example of people who may collaterally affected falls under this category. It's just an example of using the word private to equate secret.