Senior Member

Sydney
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Join Date:Joined: Aug 2013
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A dirty flash means not wiping System partition. I have seen a lot of people who wipe more than they should during a dirty fl;ash. If the ROM ZIP is a properly working standard standard custom ROM, it works.
As for "keeping something around that's not being used", when the dirty flash works as it is designed, it means not having to uninstall the APK every time a new version of the ROM is released and flashed. It stays frozen/hidden.