That is true, so you have to crawl them manually.
Crawling the authenticated section of the site with an automated crawler is very ineffecient and even dangerous.
Post-authenticated sections of the site have complex logic and critical functionality, an automated crawler calling these functions without understanding them is a bad idea.
That is why it is best that you do the crawling manually for these sections and then let the scanner scan only those sections of the site that you feel are safe. At this point you can use Session Plugins to help you handle authentication. More details about session plugins are available here -
http://ironwasp.org/learn/CustomSessionPlugin.html
The next version of IronWASP will make it very easy to create session plugins, even without any programming knowledge :)
Hope this helps!
Cheers,
Lava