Privacy Browser Android

Hello, I discovered a strange behaviour concerning the cache clean-up mechanism. Steps:

1. Do a fresh install of Privacy Browser and start it
2. Open settings, check "Enable JavaScript by default" and change the User agent to "Firefox 48 on Android 6.0.1"
3. Go to https://mobile.twitter.com/support and wait for the page to load (tap on the shield to enable JavaScript if the page won't load)
4. Bookmark the page for convenience
5. Now, disconnect the device from the Internet: Wi-Fi, mobile data and everything. Go offline.
6. Close the browser using "Clear and Exit"
7. Through Android settings, force close Privacy Browser. Clear the Cache and reboot the device if you want
8. Restart Privacy Browser and open the previously created bookmark

A ghost of the Twitter website will show up, with icons, buttons and cookie bar. From where it came from? Why the browser does not simply show an error saying that there is no Internet and so it can't load the URL?

I think the culprit here is the WebView, and maybe... IndexedDB or similar? The only way I found to delete that strange cache, is to clear all the Privacy Browser data through Android settings. Other WebView based browsers do the same thing (Lightning). Can you investigate on this? Thanks!