This project is used by volunteers to request special sysadmin permissions that require the signature of a non-disclosure agreement with the Wikimedia Foundation. For more details, check wikitech:Volunteer NDA.
Reasons for restricted policy:
Members of Operations, WMF-Legal, and @Qgil (ECT in Phabricator can be joined by All Users) are the gatekeepers of the Volunteer NDA process. Being member of the WMF-NDA-Requests project simply will give users access to the NDA. It is expected that most of the times this project will have 0 members or just 1.