Does Tor save thumbnails of frequently visited…

Tor is based on Firefox, which by default stores thumbnails of your most visited websites (literally a screenshot of the webpage) and displays it on the start page and new tab page. Seeing how Tor takes disk avoidance so seriously and tries not to record any browsing activity to disk, is this feature turned off? Are temporary screenshots of websites you visit stored to disk when you use Tor, even for an instant?

I ask because the UI elements that that Firefox uses to show you frequently visited websites are still present in Tor, but are blank.

Found here