Not necessarily. Browser extension APIs have to provide APIs for the way ads are loaded. For example if they are magically loaded, chrome needs to give you an API to intercept magic. I'm not sure if chrome requests API allows you to block websockets, but maybe it's possible to load ads over websockets and Adblock would be unable to interfere. Even if it is not possible, there's probably a lot of ways to abuse Adblock to make it do a much worse job.