the terms of service links to the privacy policy to explain how private repos are treated, the privacy policy is equally binding. from your link:

> Short version: We treat the content of private repositories as confidential, and we only access it as described in our Privacy Statement—for security purposes, to assist the repository owner with a support matter, to maintain the integrity of the Service, to comply with our legal obligations, if we have reason to believe the contents are in violation of the law, or with your consent.