Not a stretch at all, it is perfectly reasonable to consider an app and an website embedded by the app as two completely different things. First there is no guarantee the WebView will open to a website owned/operated by the same entity that owns/operates the app, so it is definitely "outside the app". From the user's privacy perspective, you also want to communicate that just because the website might be branded "Facebook" and be run by Facebook and maybe you trust FB with your messages, but if it's an embedded browser opened via a WebView then the app can technically snoop on the private message you are typing into the WebView
It doesn’t say “outside of the app”. It says “information about the content you have viewed, which is not part of the app, such as websites”, which is completely different.
This category exists for apps that embed a webview.
Safari is sandboxed. There is no way to get to its data like history.