I'm not well versed into adblocking, but shouldn't the extension also get access to the content of the request as well, to be able to either improve it's blocki

I'm not well versed into adblocking, but shouldn't the extension also get access to the content of the request as well, to be able to either improve it's blocking accuracy (e.g. detect if the whitelisted content matches blocked content patterns) or decide to hide a resource after it was fetched ?