Completely irrelevant, you're missing the use case. When you're using embedded web renderer, the point is that you are in control of the content, hence there's

Completely irrelevant, you're missing the use case. When you're using embedded web renderer, the point is that you are in control of the content, hence there's 0 security concern. If you don't control the content, then you're not secure with either WebView nor GeckoView.