Good! Webviews are browsers. Browsers are webviews. There’s no way to tell the difference, because there is no difference!
When you put a webview in an app, the app is the browser. Period. A browser is by definition an app that displays webviews. And yes, a browser can access and modify the webpages it is displaying, no shit. That’s literallt the job of the browser, aka the user agent.
So you're saying that laypeople shouldn't be allowed to create new browsers that interact with the Web in whatever way they want to? Why exactly?