Confirmed, it's in X3 (just used it two nights ago as a vocoder on a cover version of "Can't Explain," soit still has that functionality). I do think you need to run Sonar as an admin for Pentagon to show up, though. I changed the properties for the Sonar shortcut so it always runs as admin so I wouldn't have to think about it any more.
If that doesn't solve it, do a custom install from Sonar X3 and check
only Pentagon.