Referrer-Policy is one the security focused HTTP headers checked during Observatory by Mozilla scans. Scott Helme talks about this in A new security header: Referrer Policy, but his comment that you can set Referrer Policy via the Content Security Policy is based on a CSP: referrer feature that had been deprecated.
Referrer-Policy: no-referrer is effectively setting rel=noreferrer on every link and protects the most against information leakage.
Applications that need
Referer header values sent to themselves should consider