Unfortunately, while Privacy Pass on paper may be privacy protecting (though there is very little research into the topic due to it's relative lack of use), jus

Unfortunately, while Privacy Pass on paper may be privacy protecting (though there is very little research into the topic due to it's relative lack of use), just by installing and using it with Tor you have reduced your effective privacy (because it's not installed in the Tor Browser by default). And the Tor folks aren't willing to include it by default for a variety of reasons (disagreeing with CloudFlare restricting visitor's ability to read pages in the first place, lack of conclusive research into how it will impact the fingerprinting of Tor users, and just general bad blood between the Tor and CloudFlare folks). Obviously, folks can do whatever they want but I wouldn't recommend using Privacy Pass over Tor for the above reasons.