[WriteOn]

Ratzinger wrote the preface

Ratzinger didn't join the SSPX.

[ultima ratio]

"Ratzinger didn't join the SSPX."

No, but he knows something's very wrong. And he was the one who reversed the Honolulu bishop's excommunication of six Catholics who supported SSPX and attended the Society's Masses. He informed the bishop the six were not guilty of a schismatic act.