Yes, to the default settings.
IMHO, I don't think resetting to the browser's default/shipping features is necessary — but I guess I could understand if your perspective is that the ("your" ) defaults are carefully chosen to give the best UX.
In that case I could see a simple, singular "Reset" button per Preference pane might be a less "busy" option that appending the (x) 'reset' button next to each divergent setting.
…but, ultimately I guess in practice the (x) per divergent General Setting wouldn't be that bad, or overwhelming, as it's unlikely to be many individual settings, for anyone but the most committed 'configure-er'!
So, "yeah" in the end, could see it extending to all settings, which would be consistent across the app, and also give more clue/training to users, for when they first notice the reset on on Website Settings.