Can blocking_session in v$session reflect X mode holder of the mutex --"cursor: pin S wait on X" ？

When "cursor: pin S wait on X" event occurs I always need to quickly find the blocker.  MOS has taught us many ways to find it. Here is the easiest one I think.

snippet from MOS 1298015.1

• In 11g onwards session holding the mutex is shown in the BLOCKING_SESSION column of <View:V$SESSION> for the waiting session.
  One can find the blocking session using SQL of the form

SELECT SQL_ID, ACTION, BLOCKING_SESSION, BLOCKING_SESSION_STATUS

   FROM v$session

  WHERE SID=&SID_OF_WAITING_SESSION;

But in practice, I found that it didn't work the blocking_session column in v$session was always null even when "cursor: pin S wait on X" happened.