Thanks, Joe. I think this is probably a bug, then. Our webmaster went to demo.mojoportal.com and set it to use artisteer-30headermenu (in the repository it has EnableNonClickablePageLinks="true", so I assume this is the same on the demo site). She created a Test page at the root level with a couple of pages under it, and marked the test page as unclickable, but it can still be clicked.
The test may still be out there by the time you get this.