But there is a significant difference. Browser is an impenetrable sandbox, while Webview can be accessed and modified by the app in many ways.
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?