There's some confusion here. WordPress themes and plug-ins don't
rely on the built-in web editor. That's why it can be safely disabled.
What that guy did is no different from sshing into the prod server, live editing a Django plug-in and refreshing the browser.
Version control of the plug-in won't protect from that. But it's a handy tool to manage regressions.
Rolling back changes and editing a live plug-in are different problems.