Not yet sure if relevant, but the default value for securePagesWithPragma has been changed from true to false between Tomcat 6 and 7…
Looks like adding the recommended line (with "false") with Tomcat 7 is no longer required.
Worst, it might break the authentication mechanism of the manager webapp.
No more time to test different version. I'm not sure this conflict I was talking about still make sense !