Clarify optional information returned from securing mechanisms.

Co-authored-by: Dave Longley <[email protected]>

index.html

@@ -2048,10 +2048,9 @@ <h3>Securing Mechanisms</h3>
           </li>
           <li>
 MUST provide a verification mechanism that returns only the information in the
-<a>conforming document</a> that has been secured and MAY provide additional
-information that might be helpful to developers. For the avoidance of doubt,
-the securing mechanism specification MUST NOT return any information that was
-not secured in the <a>conforming document</a>. The concrete interface that is
+<a>conforming document</a> that has been secured. It MAY provide an
+additional mechanism to receive other information that might be helpful
+to developers. The concrete interface that is
 expected to be provided is detailed in the
 <a href="#verify-securing-mechanism">securing mechanism verification
 algorithm</a> section.