Does the browser still stores the website you visited Private Browsing [incognito Firefox]?

As they clearly state in their website they mention that

What does Private Browsing not save?

• Visited pages: No pages will be added to the list of sites in the History menu, the Library window's history list, or the Awesome Bar address list.


• Cached Web Content and Offline Web Content and User Data: No temporary Internet files (cached files) or files that websites save for offline use will be saved.

Considering this Scenario

If I open a tab in incognito Mode as per below screenshot.

After I close the tab It gives me an option to Undo Close Tab and If I click on it,This restores the tab which I closed.!

So Does this mean that this statement is untrue? Cached Web Content and Offline Web Content and User Data: No temporary Internet files (cached files) or files that websites save for offline use will be saved

Further research regarding this

I opened the about:config from Firefox and I filtered browser.sessionstore.and I'm setting the following preferences as follows,and now closed tab will no longer will be able to perform undo

• browser.sessionstore.max_tabs_undo;0


• browser.sessionstore.max_windows_undo;0

According to Firefox

The saved session data is also cleared upon receiving the "browser:purge-session-history" notification.

The data is stored on disk as a serialized javascript data structure (though it's possible that it will be converted to JSON once that becomes natively supported by Gecko/Spidermonkey)