You can easily block elements inside a web page or you can inspect them and see (with browser tools!) what network requests they perform. If the elements are part of the browser chrome, you need quite a lot more efford.

I would guess one key distinction is that an adblocker could block the ad injected to the page, but not one that's in the browser chrome.

How is it inside the webpage? Opera's ads have been in their toolbar for over a decade, themed the way the browser is and obviously distinct from the WebView. This isn't news

I didn't like it, so I don't use it. Most people don't like it, most people don't use it

Have you seen the screenshot?