Just about, yup! I don't know about your specific link there, but the "zero knowledge" part comes from the token sent to the provider being non-reversible. A t

Just about, yup! I don't know about your specific link there, but the "zero knowledge" part comes from the token sent to the provider being non-reversible. A token cannot be used to identify the person who generated the token, even by ID validator. This works because the token is just used as material in (simplified) a hash function.